NKG2D receptor signaling shapes T cell thymic education

The role of natural killer group 2D (NKG2D) in peripheral T cells as a costimulatory receptor is well established. However, its contribution to T cell thymic education and functional imprint is unknown. Here, we report significant changes in development, receptor signaling, transcriptional program, and function in T cells from mice lacking NKG2D signaling. In C57BL/6 (B6) and OT-I mice, we found that NKG2D deficiency results in Vβ chain usage changes and stagnation of the double-positive stage in thymic T cell development. We found that the expression of CD5 and CD45 in thymocytes from NKG2D deficient mice were reduced, indicating a direct influence of NKG2D on the strength of T cell receptor (TCR) signaling during the developmental stage of T cells. Depicting the functional consequences of NKG2D, peripheral OT-I NKG2D-deficient cells were unresponsive to ovalbumin peptide stimulation. Paradoxically, while αCD3/CD28 agonist antibodies led to phenotypic T cell activation, their ability to produce cytokines remained severely compromised. We found that OT-I NKG2D-deficient cells activate STAT5 in response to interleukin-15 but were unable to phosphorylate ERK or S6 upon TCR engagement, underpinning a defect in TCR signaling. Finally, we showed that NKG2D is expressed in mouse and human thymic T cells at the double-negative stage, suggesting an evolutionarily conserved function during T cell development. The data presented in this study indicate that NKG2D impacts thymic T cell development at a fundamental level by reducing the TCR threshold and affecting the functional imprint of the thymic progeny. In summary, understanding the impact of NKG2D on thymic T cell development and TCR signaling contributes to our knowledge of immune system regulation, immune dysregulation, and the design of immunotherapies.

Reduced Time to Surgery and Prophylactic Fasciotomy May Result in Improved Outcomes in Popliteal Artery Injuries

BACKGROUND

Popliteal artery injuries are uncommon and often result in limb loss or long-term limb dysfunction. The aims of this study were (1) to evaluate the association between predictors and outcomes and (2) to validate the rational of systematic early fasciotomy.

METHODS

This retrospective cohort study included 122 patients (80% men, n = 100) who underwent surgery for popliteal artery injuries from October 2018 to March 2021 in southern Vietnam. Primary outcomes included primary and secondary amputation. The associations between predictors and primary amputation were analyzed using logistic regression models.

RESULTS

Among the 122 patients, 11 (9%) underwent primary amputation, while 2 (1.6%) had secondary amputation. Longer time to surgery was associated with increased odds of amputation (odds ratio = 1.65; 95% confidence interval, 1.2 to 2.2 for every 6 hr). Severe limb ischemia was also associated with a 50-fold increase in the risk of primary amputation (adjusted odds ratio = 49.9; 95% confidence interval, 6 to 418, P = 0.001). Furthermore, 11 patients (9%) without signs of severe limb ischemia and acute compartment syndrome on admission were found to have myonecrosis of at least one muscle compartment during fasciotomy.

CONCLUSIONS

The data suggest that among patients with popliteal artery injuries, prolonged time before surgery and severe limb ischemia are associated with increased risk of primary amputation, whereas early fasciotomy may lead to improved outcomes.

Left renal vein as a graft for aortic reconstruction in a patient with primary aortoenteric fistula secondary to a mycotic aneurysm

Description of the use of the left renal vein for aortic reconstruction in primary aortoenteric fistula secondary to a mycotic aneurysm has not been found in the literature. We report here a case of primary aortoenteric fistula secondary to a mycotic aneurysm with gross retroperitoneal contamination that was successfully treated by using a left renal vein graft for aortic reconstruction.

Eustachian Tube Balloon Dilation: A Systematic Review and Meta-analysis of Treatment Outcomes

OBJECTIVE

To examine the effectiveness of eustachian tube balloon dilation for the treatment of eustachian tube dysfunction.

DATA SOURCES

PubMed, Scopus, and Google Scholar.

REVIEW METHODS

A systematic review of eustachian tube balloon dilation for the treatment of eustachian tube dysfunction was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines to identify randomized control trials and prospective and retrospective studies published prior to January 31, 2019. Meta-analysis of proportions evaluated 7-item Eustachian Tube Dysfunction Questionnaire (ETDQ7) scores, tympanometry, otoscopy findings, and the ability to perform a Valsalva maneuver.

RESULTS

The systematic review identified 35 studies. Twelve studies met inclusion for meta-analysis (448 patients). Mean ETDQ7 scores decreased by 2.13 from baseline to 6 weeks (95% CI, -3.02 to -1.24; P < .001). From baseline to 6 weeks, 53.0% of patients had improvement in tympanograms (P < .001). At the long-term point (3-12 months), 50.5% of patients had improved tympanograms from baseline (P < .001). There was no significant difference in the proportion of improved tympanograms at 6 weeks compared to long term (P = .535). Normal otoscopy exams at baseline increased by 30.0% at 6 weeks (P < .001) and 55.4% in the long term (P < .001). There was a 67.8% increase in proportion of patients able to perform a Valsalva maneuver in the long term compared to baseline (P < .001).

CONCLUSION

Eustachian tube balloon dilation appears to be associated with improvement in subjective and objective treatment outcome metrics. The improvement appears stable at 3 to 12 months after dilation. Patients with eustachian tube dysfunction are likely to benefit from balloon dilation, particularly those with medication-refractory disease.

Systematic Review and Meta-analysis of SNOT-22 Outcomes after Surgery for Chronic Rhinosinusitis with Nasal Polyposis

Objective Wide variation exists regarding reported outcomes after endoscopic sinus surgery (ESS) for chronic rhinosinusitis with nasal polyps (CRSwNP). This study seeks to combine data across studies to generate a summary measure and explore factors that might lead to variation. Data Sources OVID Medline, Scopus, EbscoHost, Database of Abstracts and Reviews of Effects, Health Technology Assessment, and National Health Service Economic Evaluation Database. Review Methods A search was performed following the PRISMA guidelines. Two independent researchers conducted a search using the mentioned data sources. Studies published before August 29, 2016, that involved ESS to treat CRSwNP were included. Mean changes in Sinonasal Outcome Test-22 (SNOT-22) scores were determined through metaregression of the following independent variables: publication year, sex, age, allergy status, asthma, tobacco use, prior surgery, follow-up length, and preoperative SNOT-22. Results Fifteen articles with 3048 patients treated with ESS met inclusion criteria. Pooled analyses of SNOT-22 scores revealed a mean change of 23.0 points (95% CI, 20.2-25.8; P < .001). A metaregression of patient factor effects on the mean change of SNOT-22 scores demonstrated that age ( r = 0.71, P = .01), asthma ( r = 0.21, P = .01), prior ESS ( r = 0.29, P = .01), and preoperative SNOT-22 score ( r = 0.4, P < .01) correlated with greater improvement in SNOT-22 scores. Tobacco use ( r = -0.91, P = .01) and longer lengths of follow-up ( r = -0.45, P < .01) were associated with less improvement in SNOT-22 scores. Conclusions Quality-of-life outcomes are significantly improved after ESS among patients with CRSwNP. Patient-specific factors may affect the degree of SNOT-22 change after surgery.

Titanium Ossicular Chain Reconstruction Revision Success and Preoperative Factors Predicting Success

Objective Determine rates of success after revision titanium ossicular chain reconstruction with either partial or total ossicular replacement prosthesis and assess preoperative factors predicting positive outcomes. Study Design Case series with planned data collection. Setting Tertiary hospital. Subjects and Methods The charts of 76 surgical patients who underwent revision titanium ossicular chain reconstruction from 2003 to 2014 were abstracted from a prospectively maintained database at the Medical University of South Carolina. Postoperative air-bone gap (ABG) after revision surgery at short-term (<6 months) and intermediate to long-term (>1 year) follow-up and preoperative factors associated with postoperative ABG ≤20 dB were recorded. A paired t test or Wilcoxon signed-rank sum test was utilized to compare preoperative, short-term, or intermediate to long-term results. Results Seventy-six patients underwent revision ossiculoplasty and met inclusion criteria. Mean postoperative ABG was 22.5 at short-term follow-up ( P < .0001) and 24.4 at intermediate to long-term follow-up ( P = .003). Postoperative ABG ≤20 dB was achieved in 51.5% of patients. The only preoperative factor associated with postoperative ABG ≤20 dB was location of original primary ossiculoplasty ( P = .01). Conclusions This is one of the larger studies involving revision titanium ossiculoplasty. Revision surgery showed a significant improvement in postoperative ABG. The location of the original ossiculoplasty correlated with success of revision surgery (defined as postoperative ABG ≤20 dB). Patients who had the primary ossiculoplasty at an outside hospital may have better audiometric outcomes than patients who had it at a tertiary hospital.

IL22 regulates human urothelial cell sensory and innate functions through modulation of the acetylcholine response, immunoregulatory cytokines and antimicrobial peptides: assessment of an in vitro model

Human urinary disorders are generally studied in rodent models due to limitations of functional in vitro culture models of primary human urothelial cells (HUCs). Current HUC culture models are often derived from immortalized cancer cell lines, which likely have functional characteristics differ from healthy human urothelium. Here, we described a simple explant culture technique to generate HUCs and assessed their in vitro functions. Using transmission electron microscopy, we assessed morphology and heterogeneity of the generated HUCs and characterized their intercellular membrane structural proteins relative to ex vivo urothelium tissue. We demonstrated that our cultured HUCs are free of fibroblasts. They are also heterogeneous, containing cells characteristic of both immature basal cells and mature superficial urothelial cells. The cultured HUCs expressed muscarinic receptors (MR1 and MR2), carnitine acetyltransferase (CarAT), immunoregulatory cytokines IL7, IL15, and IL23, as well as the chemokine CCL20. HUCs also expressed epithelial cell-specific molecules essential for forming intercellular structures that maintain the functional capacity to form the physiological barrier of the human bladder urothelium. A subset of HUCs, identified by the high expression of CD44, expressed the Toll-like receptor 4 (TLR4) along with its co-receptor CD14. We demonstrated that HUCs express, at the mRNA level, both forms of the IL22 receptor, the membrane-associated (IL22RA1) and the secreted soluble (IL22RA2) forms; in turn, IL22 inhibited expression of MR1 and induced expression of CarAT and two antimicrobial peptides (S100A9 and lipocalin-2). While the cellular sources of IL22 have yet to be identified, the HUC cytokine and chemokine profiles support the concept that IL22-producing cells are present in the human bladder mucosa tissue and that IL22 plays a regulatory role in HUC functions. Thus, the described explant technique is clearly capable of generating functional HUCs suitable for the study of human urinary tract disorders, including interactions between urothelium and IL22-producing cells.

Enhancing T lineage production in aged mice: a novel function of Foxn1 in the bone marrow niche

Foxn1 is essential for thymic organogenesis and T lymphopoiesis. Whereas reduced Foxn1 expression results in a decline in T lymphopoiesis, overexpression of Foxn1 in the thymus of a transgenic mouse model (Foxn1Tg) attenuates the age-associated decline in T lymphopoiesis. T lymphopoiesis begins with early T cell progenitors (ETP), derived from multipotent progenitors (MPP) in the bone marrow (BM). A decline in MPP and ETP numbers with age is thought to contribute to reduced T lymphopoiesis. Previously, we showed that reduced ETP number with age is attenuated in Foxn1 transgenic (Tg); whether the effect is initiated in the BM with MPP is not known. In this study, we report that Foxn1 is expressed in wild-type BM and overexpressed in Foxn1Tg. With age, the number of MPP in Foxn1Tg was not reduced, and Foxn1Tg also have a larger pool of hematopoietic stem cells. Furthermore, the Foxn1Tg BM is more efficient in generating MPP. In contrast to MPP, common lymphoid progenitors and B lineage cell numbers were significantly lower in both young and aged Foxn1Tg compared with wild type. We identified a novel population of lineage(neg/low), CD45(pos) EpCAM(pos), SCA1(pos), CD117(neg), CD138(neg), MHCII(neg) cells as Foxn1-expressing BM cells that also express Delta-like 4. Thus, Foxn1 affects both T lymphopoiesis and hematopoiesis, and the Foxn1 BM niche may function in skewing MPP development toward T lineage progenitors.

A potential role for B cells in suppressed immune responses in cord blood transplant recipients

We evaluated immune reconstitution in 58 adults who received hematopoietic stem cell transplants from allogeneic siblings (allosib), matched unrelated donors (MUD), or cord blood (CB) at 90-day intervals for one year post-transplant. CB recipients had a higher incidence of infections in the first 100 days compared to allosib and MUD recipients. The number of circulating T cells was lower in CB recipients compared to MUD recipients at 90 days and compared to allosib recipients at 180 days. Spectratype analysis of the TCR Vβ complementarity determining region 3 (CDR3) of patient lymphocytes revealed that the TCR repertoire remained poorly diversified even at 360 days in nearly all patients. In contrast, the number of circulating B cells was significantly elevated in CB recipients compared to allosib recipients throughout the first year post-transplant and compared to MUD recipients at 9-12 months. Spectratype analysis of the B cell receptor V_H CDR3 showed that the B cell repertoire was diversified in most patients by 90 days. CD5^pos B cells from assayed CB recipients expressed intracellular IL-10 early post-transplant. Our data suggest that B cells, in addition to T cells, may play a role in impaired immune responses in CB transplant patients.

A 7-Year Review of the Safety of Tonsillectomy during Short-Term Medical Mission Trips

Objective. To evaluate the safety of tonsillectomy in a short-term medical mission setting.

Study Design. Retrospective chart review.

Setting. Catholic mission hospital in Guatemala.

Subjects and Methods. During 7 consecutive annual mission trips from 2004 to 2010, patients received tonsillectomy and adenotonsillectomy. Established safety protocol requires candidates for tonsillectomy to agree to stay within 1 hour of the hospital for 10 days following the operation. This study includes all tonsillectomy patients regardless of age or indication for tonsillectomy. The primary outcome measures include posttonsillectomy hemorrhage, nasopharyngeal reflux, readmission for dehydration, and mortality. This is a novel study as the work performed by most short-term medical missions is unregulated and unevaluated.

Results. Medical charts were available for 197 (96.6%) of the 204 patients receiving tonsillectomy in the 7-year period; this was the only inclusion criterion. Ninety-nine (50.3%) patients had tonsillectomy concomitantly with adenoidectomy. Patients ranged in age from 3 to 66 years. The mean (SD) age was 17.2 (14.0) years. The study team found documentation of postoperative complications in 3 (1.5%) patients; 2 experienced postoperative hemorrhage, 1 within the first postoperative hour and 1 at 96 hours. The final patient returned to the hospital within 24 hours symptomatic for dehydration.

Conclusions. The authors have evaluated a protocol for tonsillectomy patients in a specific setting and believe their data represent satisfactory outcomes for the reviewed patients. The generalizability of this information is uncertain, but safety protocols should be established on all short-term medical missions to prevent untoward complications.

Mixed lineage kinase 3 modulates β-catenin signaling in cancer cells

Expression of β-catenin is strictly regulated in normal cells via the glycogen synthase kinase 3β (GSK3β)- adenomatous polyposis coli-axin-mediated degradation pathway. Mechanisms leading to inactivation of this pathway (example: activation of Wnt/β-catenin signaling or mutations of members of the degradation complex) can result in β-catenin stabilization and activation of β-catenin/T-cell factor (TCF) signaling. β-Catenin-mediated cellular events are diverse and complex. A better understanding of the cellular signaling networks that control β-catenin pathway is important for designing effective therapeutic strategies targeting this axis. To gain more insight, we focused on determining any possible cross-talk between β-catenin and mixed lineage kinase 3 (MLK3), a MAPK kinase kinase member. Our studies indicated that MLK3 can induce β-catenin expression via post-translational stabilization in various cancer cells, including prostate cancer. This function of MLK3 was dependent on its kinase activity. MLK3 can interact with β-catenin and phosphorylate it in vitro. Overexpression of GSK3β-WT or the S9A mutant was unable to antagonize MLK3-induced stabilization, suggesting this to be independent of GSK3β pathway. Surprisingly, despite stabilizing β-catenin, MLK3 inhibited TCF transcriptional activity in the presence of both WT and S37A β-catenin. These resulted in reduced expression of β-catenin/TCF downstream targets Survivin and myc. Immunoprecipitation studies indicated that MLK3 did not decrease β-catenin/TCF interaction but promoted interaction between β-catenin and KLF4, a known repressor of β-catenin/TCF transcriptional activity. In addition, co-expression of MLK3 and β-catenin resulted in significant G(2)/M arrest. These studies provide a novel insight toward the regulation of β-catenin pathway, which can be targeted to control cancer cell proliferation, particularly those with aberrant activation of β-catenin signaling.

Indication of electron neutrino appearance from an accelerator-produced off-axis muon neutrino beam

The T2K experiment observes indications of ν(μ) → ν(e) appearance in data accumulated with 1.43×10(20) protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with |Δm(23)(2)| = 2.4×10(-3)  eV(2), sin(2)2θ(23) = 1 and sin(2)2θ(13) = 0, the expected number of such events is 1.5±0.3(syst). Under this hypothesis, the probability to observe six or more candidate events is 7×10(-3), equivalent to 2.5σ significance. At 90% C.L., the data are consistent with 0.03(0.04) < sin(2)2θ(13) < 0.28(0.34) for δ(CP) = 0 and a normal (inverted) hierarchy.

A human thymic epithelial cell culture system for the promotion of lymphopoiesis from hematopoietic stem cells

OBJECTIVE

A human thymic epithelial cell (TEC) line expressing human leukocyte antigen-ABC and human leukocyte antigen-DR was engineered to overexpress murine Delta-like 1 (TEC-Dl1) for the purpose of establishing a human culture system that supports T lymphopoiesis from hematopoietic progenitor cells (HPCs).

MATERIALS AND METHODS

Cord blood or bone marrow HPCs were co-cultured with either the parental TEC line expressing low levels of the Notch ligands, Delta-like 1 and Delta-like 4, or with TEC-Dl1 to determine if these cell lines support human lymphopoiesis.

RESULTS

In co-cultures with cord blood or bone marrow HPCs, TEC-Dl1 cells promote de novo generation of CD7(pos)CD1a(pos) T-lineage committed cells. Most CD7(pos)CD1a(hi) cells are CD4(pos)CD8(pos) double-positive (DP). We found that TEC-Dl1 cells are insufficient to generate mature CD3(hi) CD4(pos) or CD3(hi) CD8(pos) single-positive (SP) T cells from the CD4(pos)CD8(pos) DP T cells; however, we detected CD3(lo) cells within the DP and SP CD4 and CD8 populations. The CD3(lo) SP cells expressed lower levels of interleukin-2Rα and interleukin-7Rα compared to CD3(lo) DP cells. In contrast to the TEC-Dl1 line, the parental TEC-84 line expressing low levels of human Notch ligands permits HPC differentiation to the B-cell lineage.

CONCLUSIONS

We report for the first time a human TEC line that supports lymphopoiesis from cord blood and bone marrow HPC. The TEC cell lines described herein provide a novel human thymic stroma model to study the contribution of human leukocyte antigen molecules and Notch ligands to T-cell commitment and maturation and could be utilized to promote lymphopoiesis for immune cell therapy.

Migration of immature and mature B cells in the aged microenvironment

Studies in aged mice show that the architecture of B-cell areas appears disrupted and that newly made B cells fail to incorporate into the spleen. These observations may reflect altered migration of immature and mature B cells. Using adoptive transfer, we tested the effect of the aged microenvironment and the intrinsic ability of donor B cells from aged mice to migrate to spleens of intact hosts. Spleens of aged recipients were deficient in attracting young or old donor immature B cells. In contrast, immature and mature B cells maintained an intrinsic ability to migrate to young recipient spleens, except that as the aged immature B cells matured, fewer appeared to enter the recirculating pool. CXCL13 protein, which is necessary for the organization of B-cell compartments, was elevated with age and differences in CXCL13 distribution were apparent. In aged spleens, CXCL13 appeared less reticular, concentrated in patches throughout the follicles, and notably reduced in the MAdCAM-1(+) marginal reticular cells located at the follicular edge. Despite these differences, the migration of young donor follicular B cells into the spleens of old mice was not impacted; whereas, migration of young donor marginal zone B cells was reduced in aged recipients. Finally, the aged bone marrow microenvironment attracted more donor mature B cells than did the young marrow. Message for CXCL13 was not elevated in the marrow of aged mice. These results suggest that the aged splenic microenvironment affects the migration of immature B cells more than mature follicular B cells.

Forced-expression of Foxn1 in stromal cells maintains thymic architecture and thymopoiesis in aged mice (86.5)

The thymus is the primary site for thymopoiesis and production of naïve T cells; however, thymic function declines with age. Thymopoiesis requires continuous thymic seeding by early T cell progenitors (ETP), a progeny of the bone marrow-derived lineage marker negative, Sca1pos, c-kitpos (LSK) progenitors that express Flt3 (LSK Flt3pos). A decrease in the frequency of ETP, and in the number of LSK Flt3pos with age has been implicated as a mechanism for the decline in thymopoiesis. We have shown that a decrease in thymocyte numbers occurs as early as 3m of age and correlates with a decrease in Foxn1 expression; however, a role for Foxn1 in thymopoiesis remains unknown. Here, we show that thymi of aged Foxn1 transgenic mice (Tg) have a higher number of thymocytes and ETP compared to aged wild type mice. Forced expression of Foxn1 also rescues aged-associated alterations of thymic architecture. Unexpectedly, we found that Foxn1 is over expressed in the bone marrow (BM). While the LSK and LSK Flt3pos are reduced in aged wild type mice, these populations remain unchanged in aged Foxn1Tg. Furthermore, the aged Foxn1 Tg also have a higher number of the lineage marker negative CD90.2pos CD2pos, a population absent in the Foxn1 mutated nude mice. Thus, our data suggest that expression of Foxn1 is critical for functional thymic and BM stromal cell niches required for the survival of T cell progenitors (NIA AG023809).

Ex vivo expansion of B cells from hematopoietic stem cells to supplement cord blood transplants (141.21)

Successful cord blood (CB) transplantation in adults is hampered by low numbers of hematopoietic stem cells (HSC) and infection due to delayed establishment of immunocompetence. By performing CDR3 spectratype analysis of T and B lymphocytes from CB transplant recipients, we demonstrated that these patients do not develop a diverse repertoire until 6 months or more after transplant. To provide rapidly engrafting antigen-responsive cells to CB recipients and to increase the number of transplanted cells, we developed an in vitro system to expand lymphoid progenitors from CB HSC. CB HSC (CD34+CD45RA+CD38-) are co-cultured for one to two weeks with either HEK 293T cells or a non-tumorigenic human thymic epithelial cell line (TEC) in media supplemented with a cocktail of cytokines and growth factors. In this study, we focused on B-lineage cells (CD79a+) and found, on average, B-lineage cells expanded more than 70 fold in HEK 293T co-cultures and nearly 100 fold in TEC co-cultures. We conclude that B-lineage cells can be expanded effectively in vitro; consequently, we are testing whether these cells are functional after engraftment in NOD/SCID/IL2Rγ-/- mice. We hypothesize that compared to patients receiving HSC alone, patients receiving transplants supplemented with in vitro-generated lymphoid progenitors will become immunocompetent sooner.

Funding by NIH AI068390 (KLK) and AG023809 (PTL)

Human thymic epithelial cell (TEC) culture system for promoting T lineage commitment and development of T cells from cord blood and bone marrow stem cells (86.6)

The discovery of Delta-like-1 (Dl1)/Notch signaling as the earliest requirement for T lineage commitment and development makes it possible to generate T cells from hematopoietic stem cells in vitro. The mouse bone marrow stroma OP9 cells that overexpress Dl1is the first stroma cell line that is capable of promoting the development of both mouse and human T cells; however, a similar approach with human stroma cells has not been established. To develop a similar culture system to closely emulate human T cell development, we have generated a human TEC line from a pediatric thymus and expressed the mouse Dl1 in this line (TEC84-Dl1). The TEC84-Dl1 expresses CD104, CD29, CD49f, CD54 (ICAM-1), and CD106 (VCAM-1); these cells also express HLA-ABC and HLA-DR. When TEC84-Dl1 were co-cultured with cord blood CD34posCD45RAposCD38neg cells, we were able to generate preT/NK (CD34posCD7posCD1aneg), preT (CD34posCD7posCD1apos), immature single positive and double positive subsets; the co-culture system also generated a CD3pos subset. Similar results were also obtained with CD34pos cells isolated from adult bone marrow. Thus, our co-culture system with the human TEC provides a complete human system for replicating thymopoiesis in vitro and offers a novel tool to optimize the development of T lineage cells that would benefit cord blood and bone marrow transplant recipients (Supports: AG023809 to PL, IDPH to PS, AI068390 to KK).

The effects of microenvironment and internal programming on plasma cell survival

Two populations of plasma cells (PCs) are formed after immunization. A short-lived population in the spleen and lymph nodes provides rapid protection. A long-lived population, mainly in the bone marrow, provides lasting immunity. The mechanisms responsible for the differences in PCs life span remain largely unknown. The goal of the current study was to compare the intrinsic survival capacity of isolated short-lived (spleen) versus long-lived (bone marrow) PCs. We approached this question by using a previously established in vitro model that measures PC survival in a supportive stromal environment. Regardless of the tissue source or isolation time point after immunization, the two PC populations showed similar intrinsic ability to survive in vitro. To test differences in the stromal microenvironments, stromal cells from marrow, spleen or lymph nodes were evaluated for ability to support PCs survival. Survival of isolated PC was always greater when co-cultured with marrow stromal cells compared with those from spleen (or lymph node) despite the finding that IL-6, necessary for PC survival in culture, was secreted by all three stromal cell sources. Additionally, low expression of B-cell-activating factor belonging to the tumor necrosis factor-family was detected in all three stromal isolates. In contrast, marrow stromal cells were distinguished by cell-surface phenotype and CXC chemokine ligand (CXCL)12, IL-7 and stem cell factor expression. Although CXCL12 has been suggested as a possible survival factor for PC, addition or neutralization of CXCL12 had minimal effect on PC survival. We conclude the mechanisms regulating PC longevity appear extrinsically driven and marrow favored, but the factors that give marrow stromal cells a unique advantage remain unknown.

The serotonin-1A agonist ipsapirone prevents ethanol-associated death of total rhombencephalic neurons and prevents the reduction of fetal serotonin neurons

Previously, this laboratory showed that in utero and in vitro ethanol exposure significantly reduces developing serotonin (5-HT) neurons and that treatment with a 5-HT1A agonist such as buspirone or ipsapirone prevents the ethanol-associated loss. The present study investigated whether ethanol decreases fetal rhombencephalic neurons, including 5-HT neurons, by causing apoptosis. We also investigated whether ipsapirone prevents the ethanol-associated deficit of fetal rhombencephalic neurons by reducing apoptosis. The results of these studies strongly suggest that the ethanol-associated reduction in fetal rhombencephalic neurons that accompanies both in utero and in vitro exposure to physiological concentrations of ethanol is associated with increased apoptosis in these neurons. A physiological concentration of ethanol (i.e., 50 mM) increases apoptosis in fetal rhombencephalic neurons and decreases the number 5-HT neurons. It also appears that the 5-HT1A agonist ipsapirone provides neuroprotection to these neurons by reducing apoptosis. Another mechanism by which ethanol-associated apoptosis can be blocked is by including serum proteins in the media at a concentration of 1% or higher; this concentration of serum proteins is high in comparison to the protein concentration in cerebrospinal fluid.

Role of stromal cells and their products in protecting young and aged B-lineage precursors from dexamethasone-induced apoptosis

Bone marrow stromal cells are potent providers of stimuli that induce proliferation of B-cell precursors. We proposed that stromal cells play a role in protecting B-lineage cells from corticosteroid-induced apoptosis. We found that stromal cells protected B-cell precursors from dexamethasone-induced apoptosis, but this did not strictly correlate with interleukin-7 (IL-7) production. To determine if stromal-derived factors were involved in protection of B-cell precursors from apoptosis, we examined the activity of three lymphopoietic growth factors: IL-7, stem cell factor (SCF), and insulin-like growth factor-1 (IGF-1). Either IL-7 or IGF-1 alone protected B-cell precursors from dexamethasone-induced apoptosis. The combined activities of IGF-1 and IL-7 were additive rather than synergistic. SCF did not protect B-cell precursors from apoptosis. Aging altered the ability of B-cell precursors to respond to protective stimuli induced by IL-7 and IGF-1. Precursors from aged animals were deficient in ability to modulate expression of apoptosis regulatory genes Bax, Bcl-2, and Bcl-x in comparison to B-cell precursors from young animals. Taken together, these results suggest that stromal cells can protect B-lineage precursors from a corticosteroid-induced apoptotic signal, protection is mediated by stromal-derived cytokines, and aging decreases the ability of B-cell precursors to respond efficiently to protective stimuli.

Molecular characterization of the mouse involuted thymus: aberrations in expression of transcription regulators in thymocyte and epithelial compartments

Despite playing a critical role in the development of naive T cells, the thymus is involuted with age. Whether a single age-associated defect or multiple aberrations contribute to thymic involution remains controversial. Here, we determined molecular aberrations in the thymocyte and epithelium compartments of the aging thymus. We demonstrated that total thymocyte numbers declined with a stepwise kinetics; clear demarcations occurred at 1.5, 3, 12 and 22 months of age. By quantitative PCR, a 2.4-fold reduction in the copies of signal joint TCR-excised circle (sjTREC)/10(5) thymocytes was first detected at 3 months; no further reduction observed thereafter. Nevertheless, the combined reductions in thymocyte numbers and sjTREC/10(5) cells caused a 7-fold decrease in sjTREC/thymus by 3 months, 21-fold by 18 months and 72-fold by 22 months as compared to 1 month. We showed aberration in expression of E2A, a transcription regulator critical for TCR beta rearrangement. While E2A expression declined 3-fold by 3 months and 18-fold by 7 months, expression of LMO2, a negative regulator of E2A activities, increased 5-fold by 18 months. Interestingly, expression of pre-T alpha and its transcriptional regulator HEB were not reduced with age. Furthermore, keratin-8 expression, specific for cortical thymic epithelium, declined 3-fold by 7 months and remained stable thereafter. In contrast, Foxn1 expression was reduced 3-fold by 3 months, 16-fold by 12 months and 37-fold by 18 months. IL-7 expression was not reduced until 7 months and reached 15-fold reduction by 22 months. Thus, the data demonstrate that thymic involution results not from a single defect, but culminates from an array of molecular aberrations in both the developing thymocytes and thymic epithelials.

T cell receptor excision circle assessment of thymopoiesis in aging mice

Signal joint T cell receptor delta (TCRD) excision circles (TRECs) are episomal DNA circles generated by the DNA recombination process that is used by T lymphocytes to produce antigen-specific alpha/beta T cell receptors. Measurement of TRECs in thymocytes and peripheral blood T cells has been used to study thymus output in chickens and humans. We have developed a real-time quantitative-PCR assay for the specific detection and quantification of mouse TCRD episomal DNA circles excised from the TCRA locus during TCRA gene rearrangement (mTRECs). We found that the mouse TCRD TRECs detected with this assay were predominantly in naïve phenotype CD4(+) and CD8(+) T cells. In a series of aged mice (range 6-90-week-old) we determined the absolute number of thymocytes and the number of molecules of mTRECs/100,000 thymocytes. We found that the absolute number of thymocytes dramatically decreased with age (P<0.05) and that molecules of mTREC/100,000 thymocytes also declined with mouse age (P<0.05). Splenocytes were isolated from aging mice and the frequency of naïve phenotype CD4 and CD8 cells determined. There was a significant drop in both CD4 and CD8 naïve peripheral T cells in the aged mice over time. mTREC analysis in purified CD4(+) and CD8(+) splenocytes demonstrated a constant level of mTRECs in the CD4 compartment until age 90 weeks, while the mTRECs in the CD8 compartment fell with age (P<0.05). By combining the mouse TREC assay with T cell phenotypic analysis, we demonstrated that IL-7 administration to young mice induced both increased thymopoiesis and peripheral T cell proliferation. In contrast, IL-7 treatment of aged mice did not augment thymopoiesis, nor induce expansion of splenic T cells. Thus, thymus output continues throughout murine adult life, and the thymic atrophy of aging in mice is not reversed by administration of IL-7.

TGF-beta1 and IL-6 expression in rat pineal gland is regulated by norepinephrine and interleukin-1beta

The pineal gland is part of the neuroendocrine system that modulates immune functions. Because the gland is outside the blood-brain barrier, it is accessible to direct feedback from circulating cytokines that affect the synthesis and secretion of melatonin. Recent studies have suggested that intrinsic immunoregulatory cytokines mediate these neuro-immune interactions under the control of sympathetic innervation to the pineal. This study focused on the expression of transforming growth factor-beta1 (TGF-beta1) and interleukin-6 (IL-6), two cytokines that have important regulatory functions on both neurons and immune cells. Northern blot RNA analysis showed that TGF-beta1, but not IL-6, was expressed in freshly dissected rat pineal glands from neonatal age (1-day-old) into adults. Immunocytochemistry for TGF-beta1 in adult glands revealed localization of this protein in astrocyte-like cells. The sympathetic neurotransmitter norepinephrine (NE) increased transcript levels for both TGF-beta1 and IL-6 in adult pineal organ cultures. The effect of NE on IL-6 expression was not found in dispersed cell cultures established from neonatal pineal glands. The immunoregulatory molecule interleukin-1beta (IL-1beta) up-regulated the expression of both IL-6 and TGF-beta1 in adult pineal organ cultures, but not in neonate pineal organ cultures. These findings suggest that TGF-beta1 and IL-6 have intrinsic regulatory roles in the pineal gland and that both neural and immune factors are important mechanisms of regulation.

The role of Drosophila mushroom body signaling in olfactory memory

The mushroom bodies of the Drosophila brain are important for olfactory learning and memory. To investigate the requirement for mushroom body signaling during the different phases of memory processing, we transiently inactivated neurotransmission through this region of the brain by expressing a temperature-sensitive allele of the shibire dynamin guanosine triphosphatase, which is required for synaptic transmission. Inactivation of mushroom body signaling through alpha/beta neurons during different phases of memory processing revealed a requirement for mushroom body signaling during memory retrieval, but not during acquisition or consolidation.

Apoptosis: one of the mechanisms that maintains unresponsiveness of the intestinal mucosal immune system

Intestinal mucosa is constantly exposed to environmental AGS: Activation of lamina propria (LP) T cells by luminal Ags may lead to the production of inflammatory cytokines and subsequent mucosal inflammation and tissue damage. However, in normal circumstances, LP T cells do not respond to antigenic stimulation. The mechanisms of this unresponsiveness in healthy subjects are not fully understood. In this study, we found by in vivo analysis that, except for T cells in lymph nodules of the mucosa, 15% of LP T cells underwent apoptosis in normal individuals. In contrast, there was a marked reduction in apoptosis of LP T cells in patients with inflammatory bowel disease (Crohn's disease and ulcerative colitis) and those with specific colitis. Our findings suggest that apoptosis might be a mechanism that turns off mucosal T cell responses to environmental Ags in healthy subjects, and resistance to apoptosis could be an important cause of mucosal immune dysregulation and tissue inflammation in colitis.

Alterations in peripheral B cells and B cell progenitors following androgen ablation in mice

The production of B lymphocytes is regulated in part by physiologic levels of androgens and estrogens. While these sex hormones down-regulate B lymphopoiesis, augmentation of B lymphopoiesis occurs under conditions where androgen or estrogen levels are decreased. In this study we examine the effect of androgen ablation of male mice on B lymphopoiesis and on the phenotypic composition of peripheral B lymphocyte populations. Spleen and thymic weights are significantly increased following castration, as is the total number of peripheral blood lymphocytes. However, the absolute numbers of B cells in the periphery are selectively increased following castration; the numbers of T cells, NK cells and granulocytes remain unchanged. The increase in circulating B cells is due largely to increases in the numbers of recent bone marrow emigrants expressing a B220(lo+)CD24(hi+) phenotype and these cells remain significantly elevated in castrated mice for up to 54 days post-castration. Similar increases in the percentages of newly emigrated B cells are observed in mice that lack a functional androgen receptor (TFM:). Finally, assessments of B cell progenitors in the bone marrow revealed significant increases in the relative numbers of IL-7-responsive B cell progenitors, including cells in Hardy fractions B (early pro-B cells), C (late pro-B cells), D (pre-B cells) and E (immature B cells). These findings demonstrate that androgen ablation following castration significantly and selectively alters the composition of peripheral B cells in mice. Further, these alterations result from the potentiating effects of androgen ablation on IL-7-responsive pro-B cell progenitors.

Alterations in CD30(+) T cells in monoclonal gammopathy of undetermined significance

Monoclonal gammopathy of unknown significance (MGUS) is a monoclonal B cell expansion characterized by high levels of circulating monoclonal antibody that affects 3% of individuals over the age of 70. Although this is considered benign, a high percentage of MGUS patients develop a debilitating peripheral autoimmune neuropathy and have a significantly increased risk for progression to multiple myeloma. Here we show that the relative numbers of the CD30(+) T cell subset and levels of CD30 expression are elevated in activated lymphocytes from normal aged individuals (> or =60 years) and in MGUS patients, when compared to younger controls. PBL from MGUS patients and age-matched controls produced comparable levels of IL-6 when activated with anti-CD3 plus IL-2, and costimulation with a soluble form of CD30 ligand (sCD30L/CD8alpha) augmented anti-CD3 inducible IL-6 production similarly in both groups. However, MGUS PBL also produced measurable IL-6 when activated with sCD30L/CD8alpha alone. This capability was associated with the unique presence of CD30(+) T cells in the peripheral blood of MGUS patients. Furthermore, a higher percentage of activated MGUS T cells express CD30 when activated by incubation with idiotype-expressing autologous serum (68 +/- 13) than those activated by anti-CD3 plus IL-2 (43 +/- 7). These results indicate that quantitative alterations in CD30(+) T cells accompany aging and MGUS and that these cells may contribute to the chronic activation of B cells though the production of IL-6.

Human thymic epithelial cells inhibit IL-15- and IL-2-driven differentiation of NK cells from the early human thymic progenitors

T/NK progenitors are present in the thymus; however, the thymus predominantly promotes T cell development. In this study, we demonstrated that human thymic epithelial cells (TEC) inhibit NK cell development. Most ex vivo human thymocytes express CD1a, indicating that thymic progenitors are predominantly committed to the T cell lineage. In contrast, the CD1a(-)CD3(-)CD56(+) NK population comprises only 0.2% (n = 7) of thymocytes. However, we observed increases in the percentage (20- to 25-fold) and absolute number (13- to 71-fold) of NK cells when thymocytes were cultured with mixtures of either IL-2, IL-7, and stem cell factor or IL-15, IL-7, and stem cell factor. TEC, when present in the cultures, inhibited the increases in the percentage (3- to 10-fold) and absolute number (3- to 25-fold) of NK cells. Furthermore, we show that TEC-derived soluble factors inhibit generation of NK-CFU and inhibit IL15- or IL2-driven NK cell differentiation from thymic CD34(+) triple-negative thymocytes. The inhibitory activity was found to be associated with a 8,000- to 30,000 Da fraction. Thus, our data demonstrate that TEC inhibit NK cell development from T/NK CD34(+) triple negative progenitors via soluble factor(s), suggesting that the human thymic microenvironment not only actively promotes T cell maturation but also controls the development of non-T lineage cells such as the NK lineage.

Human small cell lung cancer cells produce brain natriuretic peptide

The tumoral production of brain natriuretic peptide (BNP) was studied using 9 small cell lung cancer (SCLC) cell lines which were established from patients with small cell lung cancer. BNP cDNA fragment was generated from 20 microg total RNA which was prepared from the human right cardiac atrium by reverse transcription-based polymerase chain reaction. Expression of BNP mRNA was detected in 30 microg total cellular RNA from these cell lines by RNase protection assays in 5 of 9 SCLC cell lines. Radioimmunoassays using 125I-radiolabeled human BNP(1-32) and antihuman BNP(1-32) antibody detected immunoreactivity in cell pellets from SCLC cell lines which had detectable BNP mRNA. BNP immunoreactivity in the cell pellets corresponds with the data from BNP mRNA analyses. We conclude that SCLC cells have detectable BNP mRNA by RNase protection assay and BNP immunoreactivity in the cells.

Altered electrophoretic migration of polycyclic aromatic hydrocarbon and styrene oxide adducts at adenine N(6) correlates with adduct-induced structural disorder

Site-specific bay region benzo[a]pyrene (7R,8S,9R,10S)-N(6)-[10-(7,8, 9,10-tetrahydro-7,8,9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadeno syl, (7S,8R,9S,10R)-N(6)-[10-(7,8,9,10-tetrahydro-7,8, 9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadenosyl, (7S,8R,9R, 10S)-N(6)-[10-(7,8,9,10-tetrahydro-7,8, 9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadenosyl, and (7R,8S,9S, 10R)-N(6)-[10-(7,8,9,10-tetrahydro-7,8, 9-trihydroxybenzo[a]pyrenyl)]-2'-deoxyadenosyl adducts, bay region benz[a]anthracene (1R,2S,3R,4S)-N(6)-[1-(1,2,3,4-tetrahydro-2,3, 4-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl and (1S,2R,3S, 4R)-N(6)-[1-(1,2,3,4-tetrahydro-2,3, 4-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl adducts, non-bay region benz[a]anthracenyl (8S,9R,10S,11R)-N(6)-[11-(8,9,10, 11-tetrahydro-8,9,10-trihydroxybenz[a]anthracenyl)]-2'-de oxyadenosyl and (8R,9S,10R,11S)-N(6)-[11-(8,9,10,11-tetrahydro-8,9, 10-trihydroxybenz[a]anthracenyl)]-2'-deoxyadenosyl adducts, and the R- and S-adducts of styrene oxide were located in the ras61 oligodeoxynucleotide and examined with respect to electrophoretic mobility. The results were compared to NMR structural data, and to site-specific mutagenesis data and in vitro DNA replication assays for the same adducts. There was a correlation between adducts having lower electrophoretic mobility and greater disorder at the adduct site as monitored by NMR. The disorder combined with the lower electrophoretic mobilities suggested that these adducts induced flexible hinge joints in the DNA rather than static bending. Usually, these were adenine N(6) adducts having S-stereochemistry at the benzylic carbon. The results also revealed a possible role for the bay region ring in stabilizing adenyl N(6) benz[a]anthracene adducts with respect to hinging at the adduct site. On the other hand, there was not a simple relationship between altered electrophoretic mobility and mutagenesis or DNA replication.

A prospective study of patients with lung cancer and hyponatremia of malignancy

This study was undertaken to define the impact of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) on sodium homeostasis in patients with lung cancer. Patients had their serum and urine electrolytes and osmolality determined before and after a saline infusion of 500 ml. The plasma hormones, AVP, ANP, plasma renin activity (PRA), angiotensin II, and aldosterone were determined by radioimmunoassay every 15 min before, during and after the saline infusion. Fifty patients, 31 with small cell lung cancer and 19 with non-small cell lung cancer participated in this trial. All 11 patients (10 patients with small cell lung cancer and one patient with non-small cell lung cancer) who presented with hyponatremia had inappropriately elevated levels of AVP. Elevated plasma AVP levels were highly correlated with the presence of hyponatremia (p < 0.00001). Initial plasma ANP levels were not associated with hyponatremia (p = 0.73). Urinary sodium concentration increased during the saline infusion proportional to the initial plasma level of ANP (p = 0.0045). AVP appears to be elevated in nearly all patients with hyponatremia of malignancy. ANP plasma levels in patients with lung cancer are associated with the ability to excrete a sodium load but do not appear to downregulate renin, angiotensin II, and aldosterone production.

TGF-beta differentially modulates epidermal growth factor-mediated increases in leukemia-inhibitory factor, IL-6, IL-1 alpha, and IL-1 beta in human thymic epithelial cells

The regulation of cytokine production by thymic epithelial cells (TEC) in the thymus is under coordinated and temporal control and is important for the development of T cells. Human TEC express TGF-beta R and epidermal growth factor (EGF) receptor, and produce TGF-beta 3 in vitro and in vivo. Furthermore, EGF has been shown to increase IL-1 alpha, IL-1 beta, IL-6 mRNA and protein levels in human TEC. Since EGF has been shown to modulate TGF-beta effector functions, we determined whether TGF-beta can modulate EGF-mediated increases in cytokine gene expression in human TEC. We established that a single TEC expresses both EGF receptor and TGF-beta R. TGF-beta plus EGF synergistically increased leukemia-inhibitory factor (LIF), additively increased IL-6, but had little effect on IL-1 alpha and IL-1 beta mRNA levels. In contrast, TGF-beta alone increased LIF and IL-6, had little effect on IL-1 alpha, and slightly decreased IL-1 beta mRNA levels. The increases in LIF and IL-6 mRNA levels by TGF-beta plus EGF correlate with the increases in LIF and IL-6 concentrations in TEC culture supernatants as detected by ELISA. We also determined the mechanism responsible for the increases in cytokine mRNA levels. TGF-beta plus EGF did not affect transcription of LIF and IL-6 genes; this suggests that the increases in the steady state levels of cytokine mRNA were mediated post-transcriptionally, most likely at the level of mRNA stability. Our data demonstrate that TGF-beta modulates TEC cytokine production. We speculate that TGF-beta produced in situ plays a role in thymocyte development by directly affecting thymocyte differentiation and by indirectly modulating TEC cytokine production.

TGF-beta differentially modulates epidermal growth factor-mediated increases in leukemia-inhibitory factor, IL-6, IL-1 alpha, and IL-1 beta in human thymic epithelial cells

The regulation of cytokine production by thymic epithelial cells (TEC) in the thymus is under coordinated and temporal control and is important for the development of T cells. Human TEC express TGF-beta R and epidermal growth factor (EGF) receptor, and produce TGF-beta 3 in vitro and in vivo. Furthermore, EGF has been shown to increase IL-1 alpha, IL-1 beta, IL-6 mRNA and protein levels in human TEC. Since EGF has been shown to modulate TGF-beta effector functions, we determined whether TGF-beta can modulate EGF-mediated increases in cytokine gene expression in human TEC. We established that a single TEC expresses both EGF receptor and TGF-beta R. TGF-beta plus EGF synergistically increased leukemia-inhibitory factor (LIF), additively increased IL-6, but had little effect on IL-1 alpha and IL-1 beta mRNA levels. In contrast, TGF-beta alone increased LIF and IL-6, had little effect on IL-1 alpha, and slightly decreased IL-1 beta mRNA levels. The increases in LIF and IL-6 mRNA levels by TGF-beta plus EGF correlate with the increases in LIF and IL-6 concentrations in TEC culture supernatants as detected by ELISA. We also determined the mechanism responsible for the increases in cytokine mRNA levels. TGF-beta plus EGF did not affect transcription of LIF and IL-6 genes; this suggests that the increases in the steady state levels of cytokine mRNA were mediated post-transcriptionally, most likely at the level of mRNA stability. Our data demonstrate that TGF-beta modulates TEC cytokine production. We speculate that TGF-beta produced in situ plays a role in thymocyte development by directly affecting thymocyte differentiation and by indirectly modulating TEC cytokine production.

Ectopic production and processing of atrial natriuretic peptide in a small cell lung carcinoma cell line and tumor from a patient with hyponatremia

BACKGROUND

Tumors and tumor cell lines from two patients with small cell lung carcinoma (SCLC) (one with and one without hyponatremia) were studied. Ectopic production and prohormone processing of atrial natriuretic peptide (ANP) were investigated to determine if a biologically active peptide was produced in a tumor cell line from a patient with hyponatremia and no evidence of arginine vasopressin (AVP) production.

METHODS

Ribonuclease (RNase) protection assays were performed on mRNA isolated from tumors and tumor cell lines established from two SCLC patients, one with and one without hyponatremia. Cellular extracts and conditioned media were studied using reversed-phase high performance liquid chromatography (HPLC) to determine the immunoreactive form of ANP. Tumor cell line sonicates were studied for subcellular localization of enzymatic activity that cleaved pro-ANP peptide substrates.

RESULTS

RNase protection assays showed a 200-base pair protected fragment in the mRNA isolated from the tumor and tumor cell line from the patient with hyponatremia (Patient 4). HPLC characterization of the cellular extract and conditioned medium from the tumor and tumor cell line from Patient 4 demonstrated ANP immunoreactivity in the same fraction as ANP- (S99-Y126). The tumor cell line extract that localizes to a subcellular fraction enriched for lysosomes and secretory organelles contains a 60-kilodalton molecular weight protein with enzyme activity that hydrolyzes synthetic pro-ANP substrates and catalyzes the formation of ANP-(S99-Y126).

CONCLUSIONS

A tumor cell line from a patient with hyponatremia was able ectopically to produce, process, and secrete ANP in the same immunoreactive form as the biologically active molecule. Preliminary studies show that tumor cell line NCI-H1284 contains an enzyme that can cleave precursors at the same amino acid sequences needed to produce ANP-(S99-Y126) from pro-ANP.

Comparison of apoptosis signaling through T cell receptor, fas, and calcium ionophore

The SUP-T13 cell line, a human T leukemia, is susceptible to apoptosis by various inducers, including anti-TCR mAb, calcium ionophores, and anti-fas mAb. Induction of apoptosis by these three agents was investigated, and several differences were found. All three agents induced DNA fragmentation with a similar time course, but the kinetics of cell death were different for the three agents. Anti-TCR mAb-induced apoptosis, but not A23187- or anti-fas-induced apoptosis, was rescued by anti-CD3 mAb treatment. In contrast, only anti-fas mAb-mediated apoptosis was rescued by PKC activators such as PMA. These differences suggest that each of these three agents mediate apoptosis by unique signaling pathways. Nevertheless, two variant subclones of SUP-T13 were found to be resistant to all three apoptosis-inducing agents, suggesting a point(s) of common regulation between the different pathways. To determine whether this regulation occurred through bcl-2, p53, or c-myc, their expression in the parental and variant cells was determined. The three clones expressed approximately equal amounts of these proteins, and their levels did not change significantly upon treatment with anti-TCR or anti-TCR plus anti-CD3 mAb. Thus, although the proximal signaling by various apoptosis inducers were quite different, a common mediator(s) (as yet unknown) may still regulate apoptosis induced by these multiple agents.

Human thymic epithelial cells produce TGF-beta 3 and express TGF-beta receptors

TGF-beta affects proliferation, differentiation and maturation of T cells; however, the effect of TGF-beta on thymic stromal cells has not been characterized. To better understand the role of TGF-beta in T cell development, we determined whether TGF-beta is present in the human thymus, and identified stromal cells that express TGF-beta receptors and respond to TGF-beta. We demonstrate that primary cultured human thymic epithelial cells (TEC) express TGF-beta 1, TGF-beta 2 and TGF-beta 3, as well as TGF-beta type I receptor (T beta RI) (ALK-5) and TGF-beta type II receptor (T beta RII) transcripts. In vitro, epidermal growth factor (EGF) increases transcript levels of TGF-beta 1, TGF-beta 3 and T beta RII, suggesting that EGF may modulate TGF-beta responses in TEC; however, TGF-beta 2 and T beta RI transcript levels were not affected. We also detect TGF-beta 3 and T beta RII protein in association with keratin-positive TEC in vitro and in vivo. TEC culture supernatants contain TGF-beta 3 as detected by Western blots and, upon heat and acid activation, display growth inhibitory activity on the CCL-64 cells that is neutralized by anti-TGF-beta mAb treatment. We further demonstrate that TGF-beta 1 increases leukemia inhibitory factor transcript levels in TEC, indicating that TEC express functional TGF-beta receptors. Thus, we have shown in the human thymus that TEC produce TGF-beta 3 and express T beta RI and T beta RII. The data suggest that TGF-beta is present in the human thymus and may indirectly affect T cell development by regulating TEC cytokine production.

In situ detection and characterization of apoptotic thymocytes in human thymus. Expression of bcl-2 in vivo does not prevent apoptosis

Apoptosis plays a crucial role in shaping the T cell repertoire during T cell development in the thymus. The observed disappearance in the thymus of CD4+ CD8+ thymocytes with a specific TCR, and the lack of CD4+ or CD8+ single positive mature cells expressing the same TCR specificity in the periphery have led to the conclusion that deletion occurs at the CD4+ CD8+ double positive stage; however, there is no direct evidence demonstrating apoptotic CD4+ CD8+ cells in situ. Apoptosis of thymocytes in situ at other stages of T cell development has also not been reported. Using three-color immunofluorescence and flow cytometric assays on frozen human thymic tissue and freshly isolated human thymocytes respectively, we directly identify CD4+ CD8+ and CD4- CD8- thymocytes in newborn human thymus that contain intracellular fragmented DNA and are therefore apoptotic. We determine that 75% of the apoptotic thymocytes are CD4+ CD8+ double positive apoptotic thymocytes, and interestingly, that 13% are CD4- CD8- double negative thymocytes. The majority of apoptotic thymocytes in situ are detected at the cortical-medullary junction; however, apoptotic thymocytes are also found scattered throughout the cortex. Furthermore, we determine that within the apoptotic thymocyte population, 54% express the apoptotic regulatory protein bcl-2 in vivo, whereas 32% are bcl-2 negative. Thus, our in vivo data directly demonstrate that both CD4+ CD8+ and CD4- CD8- human thymocytes die in situ via an apoptotic process, and that expression of the bcl-2 protein in situ does not prevent immature thymocytes from apoptosis.

In situ detection and characterization of apoptotic thymocytes in human thymus. Expression of bcl-2 in vivo does not prevent apoptosis

Apoptosis plays a crucial role in shaping the T cell repertoire during T cell development in the thymus. The observed disappearance in the thymus of CD4+ CD8+ thymocytes with a specific TCR, and the lack of CD4+ or CD8+ single positive mature cells expressing the same TCR specificity in the periphery have led to the conclusion that deletion occurs at the CD4+ CD8+ double positive stage; however, there is no direct evidence demonstrating apoptotic CD4+ CD8+ cells in situ. Apoptosis of thymocytes in situ at other stages of T cell development has also not been reported. Using three-color immunofluorescence and flow cytometric assays on frozen human thymic tissue and freshly isolated human thymocytes respectively, we directly identify CD4+ CD8+ and CD4- CD8- thymocytes in newborn human thymus that contain intracellular fragmented DNA and are therefore apoptotic. We determine that 75% of the apoptotic thymocytes are CD4+ CD8+ double positive apoptotic thymocytes, and interestingly, that 13% are CD4- CD8- double negative thymocytes. The majority of apoptotic thymocytes in situ are detected at the cortical-medullary junction; however, apoptotic thymocytes are also found scattered throughout the cortex. Furthermore, we determine that within the apoptotic thymocyte population, 54% express the apoptotic regulatory protein bcl-2 in vivo, whereas 32% are bcl-2 negative. Thus, our in vivo data directly demonstrate that both CD4+ CD8+ and CD4- CD8- human thymocytes die in situ via an apoptotic process, and that expression of the bcl-2 protein in situ does not prevent immature thymocytes from apoptosis.

Human thymic epithelial cells: adhesion molecules and cytokine production

The ability to culture human thymic epithelial cells has greatly facilitated studies of direct cell-cell interaction between thymic epithelial cells and T lymphocytes in vitro, as well as cytokine production and regulation of cytokine production. In vitro, human thymic epithelial cells bind to T lymphocytes via two adhesion pathways: CD2-lymphocyte function-associated antigen-3 and lymphocyte function-associated antigen-1-intercellular adhesion molecule-1. Cultured human thymic epithelial cells produce interleukins-1 alpha, -1 beta, -3, -6 and -8, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, leukemia inhibitory factor and transforming growth factor-alpha. Production of thymic epithelial cell-derived cytokines is regulated by both adhesion molecules (lymphocyte function-associated antigen-3) and soluble factors via both autocrine (interleukin-1 alpha, transforming growth factor-alpha) and paracrine (interleukin-4, interferon-gamma) pathways. Transforming growth factor-alpha and epidermal growth factor regulate various cytokine mRNA at a post-transcriptional level by increasing cytokine mRNA stability.

Human small cell lung cancer cell lines express functional atrial natriuretic peptide receptors

Small cell lung cancer cell (SCLC) lines, NCI-H82, NCI-H660, and NCI-H1284, and HeLa cells were analyzed for the presence of atrial natriuretic peptide (ANP) receptors. In these SCLC cell lines and HeLa cells, ANP A receptor mRNA was identified by Southern blot analyses of polymerase chain reaction products and RNase protection assays using poly(A)(+)-selected RNA. Saturable binding assays revealed that HeLa cells had 2000 to 5000 high affinity atrial natriuretic peptide receptors per cell with a dissociation constant of 140 pM. In the SCLC cell lines, the binding was saturable but too low to accurately estimate the number of binding sites. After addition of human ANP, radioimmunoassays revealed accumulation of cyclic GMP in SCLC cells as well as HeLa cells in a dose-dependent fashion. The half-maximal stimulation concentration of cyclic GMP accumulation in HeLa and these SCLC cell lines was approximately 2 nM. Tetrazolyl blue assays and tritiated thymidine incorporation did not show any remarkable growth inhibition or growth stimulation of SCLC cell lines after addition of human ANP up to 3.3 microM, more than 1000-fold greater than the half-maximal stimulation concentration of cyclic GMP accumulation. Our results indicate that human SCLC cells express functional ANP receptors but ANP addition produced no detectable change in their growth pattern.

Atrial natriuretic factor and arginine vasopressin production in tumor cell lines from patients with lung cancer and their relationship to serum sodium

Patients with lung cancer (n = 263) were studied to determine the relationship among ectopic production of atrial natriuretic factors (ANF) and arginine vasopressin (AVP), serum sodium, and patient outcome. Of 133, 21 (16%) patients with small cell lung cancer (SCLC) had hyponatremia (serum sodium, < 130 mmol/liter), compared to none of 130 (0%) patients with non-small cell lung cancer (P < 0.0001). Patients with extensive-stage SCLC and hyponatremia had shorter survival than patients with extensive stage SCLC and normal serum sodium values (P = 0.012). Of the 11 hyponatremic patients with SCLC and tumor cell lines available for study, 9 produced ANF mRNA, 7 of 11 produced AVP mRNA, and 5 of 11 produced both ANF mRNA and AVP mRNA. All 11 cell lines produced either ANF mRNA and ANF peptide or AVP mRNA and AVP peptide, or both. The quantity of AVP peptide in the tumor cell lines was more closely associated with hyponatremia in the patients (P = 0.0026, r2 = 0.28) than was the production of ANF peptide (P = 0.066, r2 = 0.12), although neither association was strong. All tumor cell lines studied from SCLC patients with hyponatremia produce ANF and/or AVP mRNA and peptides.

Regulation of cytokine production in the human thymus: epidermal growth factor and transforming growth factor alpha regulate mRNA levels of interleukin 1 alpha (IL-1 alpha), IL-1 beta, and IL-6 in human thymic epithelial cells at a post-transcriptional level

Human thymic epithelial (TE) cells produce interleukin 1 alpha (IL-1 alpha), IL-1 beta, and IL-6, cytokines that are important for thymocyte proliferation. The mRNAs for these cytokines are short-lived and are inducible by multiple stimuli. Thus, the steady-state levels for IL-1 and IL-6 mRNAs are critical in establishing the final cytokine protein levels. In this study we have evaluated the effect of epidermal growth factor (EGF), a growth factor for TE cells, and its homologue transforming growth factor alpha (TGF-alpha), on primary cultures of normal human TE cells for the levels of IL-1 alpha, IL-1 beta, IL-6, and TGF-alpha mRNA. We showed that TE cells expressed EGF receptors (EGF-R) in vitro and in vivo, and that treatment of TE cells with EGF or TGF-alpha increased IL-1 and IL-6 biological activity and mRNA levels for IL-1 alpha, IL-1 beta, and IL-6. Neither EGF nor TGF-alpha increased transcription rates of IL-1 alpha, IL-1 beta, and IL-6 genes, but rather both EGF and TGF-alpha increased cytokine mRNA stability. By indirect immunofluorescence assay, TGF-alpha was localized in medullary TE cells and thymic Hassall's bodies while EGF-R was localized to TE cells throughout the thymus. Thus, TGF-alpha and EGF are critical regulatory molecules for production of TE cell-derived cytokines within the thymus and may function as key modulators of human T cell development in vivo.

Thymic microenvironment induces HIV expression. Physiologic secretion of IL-6 by thymic epithelial cells up-regulates virus expression in chronically infected cells

The hallmark of infection with HIV-1 is progressive depletion and qualitative dysfunction of the CD4+ Th cell population in infected individuals. Clinical trials of antiretroviral agents have shown that, despite suppression of virus replication, regeneration of the T cell pool does not occur. One proposed explanation for the defective regenerative capacity of the CD4+ T cell pool is infection of early T lymphocyte progenitors or stem cells. An additional explanation could be failure of cells of the intrathymic microenvironment (thymic epithelial (TE) cells) to carry out critical nurturing functions for developing thymocytes, i.e., secretion of thymocyte-trophic cytokines and expression of adhesion molecules. This study examines the effect of HIV on cultured TE cells and determines the role of TE cells in the regulation of viral expression in chronically HIV-infected cells. We found no evidence of infection of TE cells after exposure to HIV-1. However, normal human serum induced secretion of IL-6 by TE cells; induction of TE IL-6 was partially blocked by anti-IFN-gamma antibodies. Moreover, supernatants from TE cells maintained in normal human serum up-regulated HIV replication in chronically HIV-1-infected cells. Because intrathymic T cell precursors can be infected with HIV and T cell precursors come into close contact with TE cells in the thymus, IL-6 secreted by TE cells during normal intrathymic development may induce HIV expression in infected thymocytes in vivo and promote the intrathymic spread of HIV.

Thymic microenvironment induces HIV expression. Physiologic secretion of IL-6 by thymic epithelial cells up-regulates virus expression in chronically infected cells

The hallmark of infection with HIV-1 is progressive depletion and qualitative dysfunction of the CD4+ Th cell population in infected individuals. Clinical trials of antiretroviral agents have shown that, despite suppression of virus replication, regeneration of the T cell pool does not occur. One proposed explanation for the defective regenerative capacity of the CD4+ T cell pool is infection of early T lymphocyte progenitors or stem cells. An additional explanation could be failure of cells of the intrathymic microenvironment (thymic epithelial (TE) cells) to carry out critical nurturing functions for developing thymocytes, i.e., secretion of thymocyte-trophic cytokines and expression of adhesion molecules. This study examines the effect of HIV on cultured TE cells and determines the role of TE cells in the regulation of viral expression in chronically HIV-infected cells. We found no evidence of infection of TE cells after exposure to HIV-1. However, normal human serum induced secretion of IL-6 by TE cells; induction of TE IL-6 was partially blocked by anti-IFN-gamma antibodies. Moreover, supernatants from TE cells maintained in normal human serum up-regulated HIV replication in chronically HIV-1-infected cells. Because intrathymic T cell precursors can be infected with HIV and T cell precursors come into close contact with TE cells in the thymus, IL-6 secreted by TE cells during normal intrathymic development may induce HIV expression in infected thymocytes in vivo and promote the intrathymic spread of HIV.

Human thymic epithelial cells produce IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor

The development of conditions for culturing normal human thymic epithelial (TE) cells free from contaminating stromal cells has allowed us to characterize a number of cytokines produced by TE cells. Using cDNA probes for human IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor (LIF), we identified mRNA for these cytokines by RNA blot analysis of total RNA preparations derived from TE cells. We demonstrated that TE cells produced IL-6 transcripts and that TE cell culture supernatants contained IL-6 biologic activity, as determined by the ability to support proliferation of the T1165 plasmacytoma line. The 1.0-kilobase (kb) transcript of granulocyte-monocyte-CSF was also detected in TE cell-derived total RNA. TE cell culture supernatants contained LIF activity, as determined by proliferation of the murine cell line DA-1a, and a 4.0-kb LIF transcript was detected in TE cell-derived total RNA preparations. The 4.0-kb LIF transcript from TE cell-derived total RNA corresponded in size to the LIF transcripts in PMA-activated T lymphocytes. Thus, using biologic assays and RNA blot analysis, we demonstrated that cultured normal human TE cells produced both immunoregulatory cytokines and cytokines that drive various differentiation stages of human hematopoiesis. Our findings support the hypothesis that TE cells may play a role in providing cytokines that are important for the proliferation and differentiation of hematopoietic precursor cells that migrate to the thymus during fetal and postnatal human thymic development.

Human thymic epithelial cells produce IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor

The development of conditions for culturing normal human thymic epithelial (TE) cells free from contaminating stromal cells has allowed us to characterize a number of cytokines produced by TE cells. Using cDNA probes for human IL-6, granulocyte-monocyte-CSF, and leukemia inhibitory factor (LIF), we identified mRNA for these cytokines by RNA blot analysis of total RNA preparations derived from TE cells. We demonstrated that TE cells produced IL-6 transcripts and that TE cell culture supernatants contained IL-6 biologic activity, as determined by the ability to support proliferation of the T1165 plasmacytoma line. The 1.0-kilobase (kb) transcript of granulocyte-monocyte-CSF was also detected in TE cell-derived total RNA. TE cell culture supernatants contained LIF activity, as determined by proliferation of the murine cell line DA-1a, and a 4.0-kb LIF transcript was detected in TE cell-derived total RNA preparations. The 4.0-kb LIF transcript from TE cell-derived total RNA corresponded in size to the LIF transcripts in PMA-activated T lymphocytes. Thus, using biologic assays and RNA blot analysis, we demonstrated that cultured normal human TE cells produced both immunoregulatory cytokines and cytokines that drive various differentiation stages of human hematopoiesis. Our findings support the hypothesis that TE cells may play a role in providing cytokines that are important for the proliferation and differentiation of hematopoietic precursor cells that migrate to the thymus during fetal and postnatal human thymic development.

Ligand binding to the LFA-3 cell adhesion molecule induces IL-1 production by human thymic epithelial cells

We have shown that human thymic epithelial (TE) cells produce IL-1 alpha, IL-1 beta, and TE cells bind to thymocytes by CD2 and LFA-1 molecules on thymocytes and LFA-3, ICAM-1 on TE cells. We investigated whether ligand binding to LFA-3 on human TE cells can modulate TE cell IL-1 production. First, we investigated the ability of human thymocytes to regulate IL-1 release by TE cells. Both autologous and allogenic emetine-treated thymocytes when cultured with TE cells augmented IL-1 release by TE cells. The augmentation of IL-1 release was cell density dependent. Inasmuch as the interaction between thymocytes and TE cells is mediated in part by CD2 molecules on thymocytes and LFA-3 molecules on TE cells we next determined the effect on IL-1 release of ligand binding (anti-LFA-3 mAb TS2/9) to TE cell surface LFA-3. Purified anti-LFA-3 mAb augmented IL-1 release in a concentration-dependent fashion. The anti-LFA-3-mediated augmentation of IL-1 release required both new protein and RNA synthesis as shown by the ability of cycloheximide and actinomycin-D to inhibit augmentation of IL-1 production by TE cells, and by direct quantitation of IL-1 alpha and IL-1 beta mRNA by Northern blot analysis. Both F(ab)'2 and Fab' fragments of anti-LFA-3 mAb augmented IL-1 alpha and IL-1 beta mRNA production, indicating that monovalent binding to cell surface LFA-3 was sufficient to provide the inducing signal. The identification of LFA-3, the cell surface ligand for thymocyte CD2 molecules, as a molecule via which TE cell-derived cytokine production may be regulated suggests a mechanism at the cell surface by which direct TE cell-thymocyte interaction might result in the triggering of local IL-1 release within the human thymic microenvironment.