Compartmentalization of the peripheral immune system

Long-distance microbial mechanisms impacting cancer immunosurveillance

The intestinal microbiota determines immune responses against extraintestinal antigens, including tumor-associated antigens. Indeed, depletion or gross perturbation of the microbiota undermines the efficacy of cancer immunotherapy, thereby compromising the clinical outcome of cancer patients. In this review, we discuss the long-distance effects of the gut microbiota and the mechanisms governing antitumor immunity, such as the translocation of intestinal microbes into tumors, migration of leukocyte populations from the gut to the rest of the body, including tumors, as well as immunomodulatory microbial products and metabolites. The relationship between these pathways is incompletely understood, in particular the significance of the tumor microbiota with respect to the identification of host and/or microbial products that regulate the egress of bacteria and immunocytes toward tumor beds.

Loss-of-function alleles of P2RX7 and TLR4 fail to affect the response to chemotherapy in non-small cell lung cancer

The success of anticancer chemotherapy relies at least in part on the induction of an immune response against tumor cells. Thus, tumors growing on mice that lack the pattern recognition receptor TLR4 or the purinergic receptor P2RX7 fail to respond to chemotherapy with anthracyclins or oxaliplatin in conditions in which the same neoplasms growing on immunocompetent mice would do so. Similarly, the therapeutic efficacy (measured as progression-free survival) of adjuvant chemotherapy with anthracyclins is reduced in breast cancer patients bearing loss-of-function alleles of TLR4 or P2RX7. TLR4 loss-of-function alleles also have a negative impact on the therapeutic outcome of oxaliplatin in colorectal cancer patients. Here, we report that loss-of-function TLR4 and P2RX7 alleles do not affect overall survival in non-small cell lung cancer (NSCLC) patients, irrespective of the administration and type of chemotherapy. The intrinsic characteristics of NSCLC (which near-to-always is chemoresistant and associated with poor prognosis) and/or the type of therapy that is employed to treat this malignancy (which near-to-always is based on cisplatin) may explain why two genes that affect the immune response to dying cells fail to influence the clinical progression of NSCLC patients.

Coronavirus infections: Epidemiological, clinical and immunological features and hypotheses

Coronaviruses (CoVs) are a large family of enveloped, positive-strand RNA viruses. Four human CoVs (HCoVs), the non-severe acute respiratory syndrome (SARS)-like HCoVs (namely HCoV 229E, NL63, OC43, and HKU1), are globally endemic and account for a substantial fraction of upper respiratory tract infections. Non-SARS-like CoV can occasionally produce severe diseases in frail subjects but do not cause any major (fatal) epidemics. In contrast, SARS like CoVs (namely SARS-CoV and Middle-East respiratory syndrome coronavirus, MERS-CoV) can cause intense short-lived fatal outbreaks. The current epidemic caused by the highly contagious SARS-CoV-2 and its rapid spread globally is of major concern. There is scanty knowledge on the actual pandemic potential of this new SARS-like virus. It might be speculated that SARS-CoV-2 epidemic is grossly underdiagnosed and that the infection is silently spreading across the globe with two consequences: (i) clusters of severe infections among frail subjects could haphazardly occur linked to unrecognized index cases; (ii) the current epidemic could naturally fall into a low-level endemic phase when a significant number of subjects will have developed immunity. Understanding the role of paucisymptomatic subjects and stratifying patients according to the risk of developing severe clinical presentations is pivotal for implementing reasonable measures to contain the infection and to reduce its mortality. Whilst the future evolution of this epidemic remains unpredictable, classic public health strategies must follow rational patterns. The emergence of yet another global epidemic underscores the permanent challenges that infectious diseases pose and underscores the need for global cooperation and preparedness, even during inter-epidemic periods.

Effects of skeletal unloading on the bone marrow antibody repertoire of tetanus toxoid and/or CpG treated C57BL/6J mice

Spaceflight is known to impact the immune system in multiple ways. However, its effect on the antibody repertoire, especially in response to challenge, has not been well characterized. The development of the repertoire has multiple steps that could be affected by spaceflight, including V-(D-)J-gene segment rearrangement and the selection of complementarity determining regions (CDRs); specifically, CDR3, responsible for much of the diversity in the repertoire. We used skeletal unloading with the antiorthostatic suspension (AOS) model to simulate some of the physiological effects associated with spaceflight. Animals ± AOS were challenged with tetanus toxoid (TT) and/or CpG, an adjuvant. Two weeks after challenge, bone marrow was collected and sequenced using the Illumina MiSeq 2 × 300 platform. The resulting antibody repertoire was characterized, including V-, D- (heavy only), and J-gene segment usage, constant region usage, CDR3 length, and V(D)J combinations. We detected changes in gene-segment usage in response to AOS, TT, and CpG treatment in both the heavy and light chains. Additionally, changes were seen in the class-switched VH-gene repertoire. Alterations were also detected in V/J pairing for both the heavy and light chains, and changes in CDR3 length. We also detected lower levels of CDR3 AA overlap than detected in the splenic repertoire. These results demonstrate that AOS, TT, and CpG alter the bone marrow antibody repertoire however, it is still unclear from the data whether there is a loss of host antigen-specific responsiveness because of the change in gene use.

Diagnostic value of peripheral blood immune profiling in colorectal cancer

PURPOSE

Little is known about the clinical value of peripheral blood immune profiling. Here, we aimed to identify colorectal cancer (CRC)-related peripheral blood immune cells and develop liquid biopsy-based immune profiling models for CRC diagnosis.

METHODS

Peripheral blood from 131 preoperative patients with CRC and 174 healthy controls was analyzed by flow cytometry and automated hematology. CRC-related immune factors were identified by comparing the mean values of immune cell percentages and counts. Subsequently, CRC diagnostic algorithms were constructed using binary logistic regression.

RESULTS

Significant differences were observed in percentages and counts of white blood cells, lymphocytes, neutrophils, regulatory T cells, and myeloid-derived suppressor cells (MDSCs) of patients and controls. The neutrophil/lymphocyte and Th1/Th2 ratios were also significantly different. Likewise, the percentages and counts of peripheral blood programed death 1, cytotoxic T lymphocyte antigen 4, B-and T-lymphocyte attenuator, and lymphocyte activation gene-3 were higher in patients with CRC. The binary logistic regression model included 12 variables, age, CD3+%, NK%, CD4+CD279+%, CD4+CD25+%, CD4+CD152+%, CD3+CD366+%, CD3+CD272+%, CD3+CD223+%, CD158b-CD314+CD3-CD56+%, Th2%, and MDSCs cells/µL, for the prediction of cancer. Results of retrospective and prospective evaluation of the area under the curve, sensitivity, and specificity were 0.980 and 0.940, 91.53% and 85.80%, and 93.50% and 86.20%, respectively.

CONCLUSION

Peripheral blood immune profiling may be valuable in evaluating the immunity of CRC patients. Our liquid biopsy-based immune diagnostic method and its algorithms may serve as a novel tool for CRC diagnosis. Future largescale studies are needed for better characterization of its diagnostic value and potential for clinical application.

Microbiome and Anticancer Immunosurveillance

Anticancer immune responses can be considered a desirable form of autoimmunity that may be profoundly shaped by the microbiome. Here, we discuss evidence for the microbiome's influence on anti-tumor immunosurveillance, including those that are indirect and can act at a distance, and we put forward hypotheses regarding mechanisms of how these effects are implemented. These may involve cross-reactivity between microbial and tumor antigens shaping T cell repertoires and/or microbial products stimulating pattern recognition receptors that influence the type and intensity of immune responses. Understanding how the microbiome impacts natural cancer immunosurveillance as well as treatment-induced immune responses will pave the way for more effective therapies and prophylactics.

Tolerance and Cross-Tolerance following Toll-Like Receptor (TLR)-4 and -9 Activation Are Mediated by IRAK-M and Modulated by IL-7 in Murine Splenocytes

Objective

Immune suppression during critical illness predisposes to serious infections. We sought to determine the mechanisms regulating tolerance and cross-tolerance to common pro-inflammatory danger signals in a model that recapitulates the intact in vivo immune response.

Materials and Methods

Flt3-expanded splenocytes obtained from wild-type or matching IRAK-M knockout (IRAK-M-/-), C57BL/6, male mice (8–10 weeks old) were treated repeatedly or alternately with either LPS or CpGA DNA, agonists of Toll-like receptor (TLR)-4 and -9, respectively, over successive 24-hour periods. Supernatants were collected following each 24-hour period with cytokine release (ELISA) and splenocyte IRAK-M expression (Western blot) determined. Tolerance and cross-tolerance were assessed in the absence or presence of programmed death receptor (PD)-1 blocking antibody or IL-7 pre-treatment.

Main Results

Splenocytes notably exhibited both tolerance and cross-tolerance to subsequent treatments with either LPS or CpGA DNA. The character of tolerance and cross-tolerance in this model was distinct following initial LPS or CpGA treatment in that TNFα and IFNγ release (not IL-10) were suppressed following LPS; whereas, initial CpGA treatment suppressed TNFα, IFNγ and IL-10 release in response to subsequent stimulation (LPS or CpGA). Tolerance and cross-tolerance were unrelated to IL-10 release or PD-1 but were attenuated in IRAK-M-/- splenocytes. IL-7 significantly suppressed IRAK-M expression and restored TNFα and IFNγ production without influencing IL-10 release.

Conclusions

In summary, acute immune tolerance and cross-tolerance in response to LPS or CpGA were distinct in that LPS selectively suppressed pro-inflammatory cytokine responses; whereas, CpGA suppressed both pro- and anti-inflammatory responses. The induction of tolerance and cross-tolerance in response to common danger signals was mechanistically unrelated to IL-10 or PD-1 but was directly influenced by IRAK-M expression. IL-7 reduced IRAK-M expression and attenuated immune tolerance induced by either LPS or CpGA, and thus may be useful for reversal of immune tolerance in the setting of critical illness.

Evaluation of the efficiency of human immune system reconstitution in NSG mice and NSG mice containing a human HLA.A2 transgene using hematopoietic stem cells purified from different sources

Severely immunodeficient mice such as the NOD/SCID/IL2rγ(null) (NSG) strain can be engrafted with human hematopoietic stem cells (HSCs), resulting in chimeric mice containing many components of the human immune system (Human Immune System mice or HIS mice). HIS mice can both support the replication of and recapitulate much of the immunological response to a variety of pathogens, including ones with strict human tropism, such as HIV-1. In an effort to develop a better mouse model for human infectious pathogen infection and possible immune resolution, we compared the human immune system reconstitution of NSG mice following injection with human CD34(+) HSCs purified from either fetal liver (FL) or umbilical cord blood (UCB). We analyzed reconstitution in standard NSG mice as well as a derivative of these mice containing an HLA.A2 encoding transgene (NSG.A2). HSCs from both sources effectively reconstituted hematopoietic lineages when injected into NSG mice. In marked contrast, total CD45(+) human hematopoietic cells in NSG.A2 mice were well reconstituted by HSCs from UCB but very poorly by HSCs purified from FL. Moreover, the reconstitution of T cell lineages in NSG.A2 mice by HSCs from UCB was inferior to that obtained using NSG mice. We also found that FL CD34(+) HSCs contain a much higher percentage of cells with a phenotype consistent with primitive progenitors than UCB HSCs. We discuss possible explanations for the influence of the HLA.A2 transgene on hematopoietic reconstitution using the two sources of HSCs.

Impact of enzymatic tissue disintegration on the level of surface molecule expression and immune cell function

Immunological characterization of immune cells that reside in specific anatomic compartments often requires their isolation from the respective tissue on the basis of enzymatic tissue disintegration. Applying enzymatic digestion of primary splenocytes, we evaluated the impact of collagenase and dispase, two enzymes that are commonly used for the liberation of immune cells from tissues, on the detectability of 48 immunologically relevant surface molecules that are frequently used for flow cytometric identification, isolation, and characterization of immune cell subsets. Whereas collagenase treatment had only minor effects on surface expression of most molecules tested, dispase treatment considerably affected antibody-mediated detectability of the majority of surface markers in subsequent FACS analyses. This effect was long lasting and, in case of high-dose dispase treatment, evident for the majority of surface molecules even after 24 h of in vitro culture. Of note, high-dose dispase treatment not only affected surface expression of certain molecules but also impaired antigen-specific proliferation of CD4(+) and CD8(+) T cells. Together, our data indicate that enzymatic tissue disintegration can have profound effects on the expression of a variety of cell-surface molecules with direct consequences for phenotypic analysis, FACS- and MACS-based target cell isolation, and immune cell function in cell culture experiments.

Immune maintenance of self in morphostasis of distinct tissues, tumour growth and regenerative medicine

Morphostasis (tissue homeostasis) is a complex process consisting of three circumstances: (1) tissue renewal from stem cells, (2) preservation of tissue cells in a proper differentiated state and (3) maintenance of tissue quantity. This can be executed by a tissue control system (TCS) consisting of vascular pericytes, immune system-related components--monocyte-derived cells (MDC), T cells and immunoglobulins and autonomic innervation. Morphostasis is established epigenetically, during the critical developmental period corresponding to the morphogenetic immune adaptation. Subsequently, the tissues are maintained in a state of differentiation reached during the adaptation by a 'stop effect' of MDC influencing markers of differentiating tissue cells and presenting self-antigens to T cells. Retardation or acceleration of certain tissue differentiation during adaptation results in its persistent functional immaturity or premature ageing. The tissues being absent during adaptation, like ovarian corpus luteum, are handled as a 'graft.' Morphostasis is altered with age advancement, because of the degenerative changes of the immune system. That is why the ageing of individuals and increased incidence of neoplasia and degenerative diseases occur. Hybridization of tumour stem cells with normal tissue cells causes an augmentation of neoplasia by host pericytes and MDC stimulating a 'regeneration' of depleted functional cells. Degenerative diseases are associated with apoptosis. If we are able to change morphostasis in particular tissue, we may disrupt apoptotic process of the cell. An ability to manage the 'stop effect' of MDC may provide treatment for early post-natal tissue disorders, improve regenerative medicine and delay physical, mental and hormonal ageing.

Organ-specific roles of CYP1A1 during detoxication of dietary benzo[a]pyrene

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed environmental toxicants derived from sources that include cigarette smoke, petroleum distillation, gas- and diesel-engine exhaust, and charcoal-grilled food. The gastrointestinal tract is the principal route of PAH exposures, even when inhaled. The most thoroughly studied prototype of PAHs is benzo[a]pyrene (BaP), well known to be toxic, mutagenic, and carcinogenic in various tissues and cell types. This lab has previously shown that Cyp1a1(-/-) global knockout mice treated by oral administration of BaP die at 28 to 32 days with immunosuppression, whereas wild-type mice remain healthy for 1 year on high BaP doses (125 mg/kg/day). Thus, for oral BaP, CYP1A1 is more important in detoxication than in metabolic activation. After several days of oral BaP, we found surprisingly low CYP1A1 levels in liver, compared with that in small intestine; we postulated that this finding might reflect efficient detoxication of oral BaP in proximal small intestine such that significant amounts of the inducer BaP no longer reach the liver. In the present study, many parameters were therefore compared in wild-type, Cyp1a1(-/-) global knockout, intestinal epithelial cell-specific Cyp1a1 knockout, and hepatocyte-specific Cyp1a1 knockout mice as a function of long-term oral exposure to BaP. The peak of CYP1A1 (mRNA, protein) expression in liver occurred at 12 h, whereas highly induced CYP1A1 in small intestine persisted throughout the 30-day experiment. Hepatocyte-specific Cyp1a1 knockout mice remained as healthy as wild-type mice; intestinal epithelial cell-specific Cyp1a1 knockout mice behaved like Cyp1a1(-/-) mice, dying with immunosuppression approximately 30 days on oral BaP. We conclude that small intestine CYP1A1, and not liver CYP1A1, is critically important in oral BaP detoxication.

Individual mouse analysis of the cellular immune response to tumor antigens in peripheral blood by intracellular staining for cytokines

Among the experimental animal models, mice remain the most widely used for the evaluation of immunotherapeutic strategies. Vaccines against parasites and viral antigens are commonly administered to the appropriate mouse strain which also allows testing of the therapeutic effect. Similarly, in mice transgenic for human tumor associated antigens (TAA), cancer vaccines must lead to breakage of immune tolerance to elicit a significant effect on the tumor. However, one of the major drawbacks in the monitoring of cellular immune responses induced by vaccination is that functional immunological assays require suppression of the animals to collect the spleen or lymph nodes for analysis. Here, we report the application of a rapid intracellular staining (ICS) method to quantify antigen-specific T cells responses in small volumes of murine blood. Genetic vaccination with plasmid DNA followed by electroporation (DNA-EP) and the use of adenoviral vectors (Ad) encoding CEA as a model target antigen were applied to different strains of mice. Optimal blood volume, number of lymphocytes, sensitivity and reproducibility of intracellular staining for IFN-gamma were determined both in non-tolerant/wild type mice as well as in tolerant CEA transgenic mice upon restimulation of PBMCs with CEA peptides. Groups of vaccinated mice were then sacrificed and PBMCs and splenocytes from individual animals were compared for intracytoplasmic detection of IFN-gamma and TNF-alpha. A significant correlation was observed between splenic and blood immune responses. Finally, the cellular immune response was followed over time in groups of vaccinated mice. The kinetics of IFN-gamma producing effectors were measured after priming and successive boosting with adenoviral vectors. We show that intracellular staining for mouse PBMCs is a rapid and simple method to measure antigen-specific immune responses. It does not require animal euthanasia and mirrors the response observed in lymphoid organs such as the spleen.

Patterns of CD4/CD8 T-cell ratio in dialysis effluents predict the long-term outcome of peritonitis in patients undergoing peritoneal dialysis

BACKGROUND

The peritoneal immune compartment is a microenvironment with a particular T-cell repertoire and susceptible to local inflammation. To clarify the role of T lymphocytes in peritoneal immunity, the changes in T-cell subpopulations in peritoneal dialysis effluents (PDEs), and their influence on the response to the treatment of peritonitis and on its prognosis were studied in patients undergoing long-term, continuous ambulatory peritoneal dialysis (CAPD).

METHODS

A cohort of 36 patients treated with CAPD and who had histories of peritonitis were divided into a group with rapid and a group with delayed response to antibiotics, and were followed for 3 years. CD4/CD8 T-cell ratios, T-cell cytokine mRNA expression patterns and transforming growth factor-beta1 (TGF-beta1) concentrations were examined in PDE during bouts of peritonitis. The change in 4 h D/P creatinine during the peritoneal equilibration test (PET) between year 0 and year 3 was expressed as deltaD/P creatinine.

RESULTS

The serial changes in T-cell subsets in PDE during peritonitis showed two patterns: (i) pattern 1, manifest as a progressive increase in the CD4/CD8 ratio, and associated with a rapid response to treatment; and (ii) pattern 2, manifest as a progressive decrease in the CD4/CD8 ratio, and associated with a delayed response to treatment. The major T-cell phenotypes in PDE during peritonitis were Th1-CD4(+) and Tc2-CD8(+), determined by cloning techniques, RT-PCR and double immunofluorescence staining. TGF-beta1 in the effluent was undetectable in pattern 1 after 7-8 days, but remained detectable at 2 weeks in pattern 2. Pattern 2 patients had a significantly greater decrease (deltaD/P creatinine: -0.198+/-0.086) in solute transport than pattern 1 patients (deltaD/P creatinine: -0.036+/-0.077, P<0.05).

CONCLUSIONS

These results suggest that a progressive decrease of the CD4/CD8 ratio in PDE correlates with a persistent expression of TGF-beta1, and plays a pathogenetic role in the evolution of peritonitis, PET deterioration and peritoneal fibrosis. Therefore, patterns of CD4/CD8 T-cell ratio in PDE may predict clinical outcomes of peritonitis in CAPD patients.

Secretory IgA specific for a conserved epitope on gp41 envelope glycoprotein inhibits epithelial transcytosis of HIV-1

As one of the initial mucosal transmission pathways of HIV (HIV-1), epithelial cells translocate HIV-1 from apical to basolateral surface by nondegradative transcytosis. Transcytosis is initiated when HIV-1 envelope glycoproteins bind to the epithelial cell membrane. Here we show that the transmembrane gp41 subunit of the viral envelope binds to the epithelial glycosphingolipid galactosyl ceramide (Gal Cer), an alternative receptor for HIV-1, at a site involving the conserved ELDKWA epitope. Disrupting the raft organization of the Gal Cer-containing microdomains at the apical surface inhibited HIV-1 transcytosis. Immunological studies confirmed the critical role of the conserved ELDKWA hexapeptide in HIV-1 transcytosis. Mucosal IgA, but not IgG, from seropositive subjects targeted the conserved peptide, neutralized gp41 binding to Gal Cer, and blocked HIV-1 transcytosis. These results underscore the important role of secretory IgA in designing strategies for mucosal protection against HIV-1 infection.

Characterization of graft-versus-host disease in SCID mice and prevention by physicochemical stressors

BACKGROUND

Graft versus host disease (GVHD) prevents potentially curative allogeneic stem cell transplantation from being offered to cancer patients who lack a suitably matched donor. New methods to prevent GVHD are required to allow successful transplants across major histocompatibility complex barriers.

METHODS

A model of GVHD in C.B-17 SCID mice was developed to allow the study of allo-activated donor T cells without confounding effects of host lymphocytes. The abilities of cyclosporin-A, anticytokine antibodies, and oxidative stress to prevent GVHD in this model was studied.

RESULTS

T cells from major histocompatibility-mismatched donor mice caused severe GVHD in sublethally irradiated SCID hosts that could be ameliorated by coadministration of donor bone marrow but not by cyclosporine-A or anticytokine antibodies. In contrast, three-log more T cells could be injected without clinical consequences if they had been pretreated with a combination of heat, ultraviolet light, and oxygenation. The effect was not the trivial result of donor T cell destruction because T cell reconstitution, although delayed, recovered to normal levels within 2 weeks. Protection from GVHD required oxygenation and was associated with normalization of the CD4/CD8 donor T cell ratio, recovery of host hematopoiesis, and decreased inflammatory cytokine production.

CONCLUSION

Pretreatment of donor T cells with a combination of physicochemical stressors effectively prevents GVHD caused by major major histocompatibility disparities and may facilitate the safe transplantation of patients without HLA-identical donors.

Lineage-specific differences among CD8+ T cells in their dependence of NF-kappa B/Rel signaling

Whereas most CD8+ T cells in lymph nodes and spleen express the CD8alpha beta heterodimer and depend absolutely on thymic competence for their development, a substantial population of T cells expressing CD8alpha alpha matures extrathymically. Although the existence of these CD8 sublineages is well established, relatively little is known about differences that might exist among CD8 cells in their requirement for particular transcriptional pathways during the development and maintenance of normal populations. Transgenic mice whose T lineage expresses an IkappaBalpha mutant exhibited decreased NF-kappaB signaling and a diminution in mature CD8 T cells. We now have determined that although TCR-dependent CD69 induction by CD8alpha alpha and CD8alpha beta T cells was unaffected by inhibition of NF-kappaB, TCRalpha beta CD8alpha beta T cells were preferentially reduced compared to their TCRalpha beta CD8alpha alpha or TCRgamma delta counterparts. This finding was most prominent in spleen, but was also apparent in Peyer's patches of transgenic mice. In addition, diminished antiviral cytotoxic responses of CD8alpha beta intraepithelial lymphocytes were observed after enteric reovirus infection. Taken together, these results indicate that NF-kappaB signaling is more important for the thymus-dependent TCRalpha beta CD8alpha beta population than for other CD8 lineages, and thus regulates the number, function, and normal balance of CD8 subsets in the periphery.

Immunological self/nonself discrimination: integration of self vs nonself during cognate T cell interactions with antigen-presenting cells

The hypothesis is presented that immunological integration of nonefficacious vs efficacious T cell antigen receptor (TCR) signals are foundational for self/nonself discrimination and that multiple integrative mechanisms are intrinsic to the molecular to molar organization of an adaptive immune response. These integrative mechanisms are proposed to adaptively regulate expression of costimulatory signals, such that foreign proteins are associated with the expression of costimulatory signals, whereas self-proteins are associated with the lack of costimulatory signaling. Overall, this model offers several unique contributions to the study of immunology. First, this model postulates that cognate TCR/major histocompatibility complex (MHC) interactions are sufficient to adaptively mediate immunological self/nonself discrimination. This model thereby offers a unique alternative to models that largely rely on innate immunity to prime immune discrimination. Second, the integrative model argues that the immune system can simultaneously reinforce self-tolerance and promote immunity to foreign organisms at the same time and in the same location. Many alternative models presume that pathogenic self-reactive T cells do not exist at the outset of an immune response against foreign agents. Third, the integrative model uniquely predicts relationships between immunodeficiency and autoimmune pathogenesis. Fourth, this model illustrates the regulatory advantages of cognate antigen presenting cell (APC) systems (i.e., T cell or B cell APC) compared to nonspecific APC. Cognate APC systems together with the respective clonotypic responders may comprise a fundamental "network" of lymphoid cells. Such networks would have clone-specific regulatory capabilities and may be central for immunological self/nonself discrimination. Fifth, this model provides an explanation for "infectious" tolerance without creating specialized subsets of "suppressor" or "regulatory" T cells. Each mature T cell retains the potential to reinforce tolerance or mediate immunity, depending on the specific antigenic cues present in the immediate environment.

Immunological system and Schistosoma mansoni: co-evolutionary immunobiology. What is the eosinophil role in parasite-host relationship?

Schistosomes, ancestors and recent species, have pervaded many hosts and several phylogenetic levels of immunity, causing an evolutionary pressure to eosinophil lineage expression and response. Schistosoma mansoni adult worms have capitalized on the apparent adversity of living within the mesenteric veins, using the dispersion of eggs and antigens to other tissues besides intestines to set a systemic activation of several haematopoietic lineages, specially eosinophils and monocytes/macrophages. This activation occurs in bone marrow, spleen, liver, lymph nodes, omental and mesenteric milky spots (activation of the old or primordial and recent or new lymphomyeloid tissue), increasing and making easy the migration of eosinophils, monocytes and other cells to the intestinal periovular granulomas. The exudative perigranulomatous stage of the periovular reaction, which present hystolitic characteristics, is then exploited by the parasites, to release the eggs into the intestinal lumen. The authors hypothesize here that eosinophils, which have a long phylogenic story, could participate in the parasite-host co-evolution, specially with S. mansoni, operating together with monocytes/macrophages, upon parasite transmission.

Expression of CD3 epsilon, CD3 zeta, and RAG-1/RAG-2 in decidual CD56+ NK cells

In early pregnancy the uterine mucosa, the decidua, is infiltrated by numerous CD56bright, CD16- natural killer (NK) cells. In this paper we have shown that unlike adult peripheral blood NK cells these uterine NK cells express cytoplasmic CD3 and CD3 zeta, but CD3 gamma and CD3 delta were not found in the majority of cells. In contrast to previous reports, there was no evidence of RAG-1 nor RAG-2 expression in decidual NK cells. These findings have implications for the ontogeny and development of decidual NK cells.

Cell-mediated immunity in experimental Trypanosoma cruzi infection

Infection of humans with the protozoan Trypanosoma cruzi leads to Chagas disease, or American trypanosomiasis, a disease that affects nearly 20 million people, and constitutes one of the largest socioeconomic burdens in Latin America. Much of the present knowledge on pathogenic mechanisms underlying T. cruzi infection comes from experimental murine models. Here, George A. DosReis reviews recent findings about the features of host cell-mediated immunity against the parasite and possible mechanisms leading to chronic infection.

Outer periarteriolar lymphoid sheath arrest and subsequent differentiation of both naive and tolerant immunoglobulin transgenic B cells is determined by B cell receptor occupancy

T-dependent B cell responses in the spleen are initiated in the outer periarteriolar lymphoid sheath (PALS) and culminate in the generation of proliferative foci and germinal center reactions. By pulsing anti-hen egg lysozyme (HEL) immunoglobulin transgenic (IgTg) B cells with various concentrations of HEL in vitro before adoptive transfer into normal recipients, it was shown that a critical number of B cell receptors (BCRs) must be ligated for B cells to undergo arrest in the outer PALS. T cell help was manipulated independently of the BCR stimulus by incubating B cells expressing the appropriate major histocompatibility complex class II antigen with a peptide recognized by CD4(+) TCR Tg T cells. B cells which either failed to arrest in the outer PALS due to a subthreshold BCR stimulus, or arrested only transiently due to the brevity of the BCR stimulus, underwent an abortive response within the follicles when provided with T cell help. In contrast, naive B cells stimulated by a sustained, suprathreshold concentration of either foreign or self-antigen and given T cell help, proliferated in the outer PALS and then differentiated. Outer PALS arrest was not influenced by the nature of the B cells occupying the follicle, but appeared to be determined solely by the magnitude of BCR stimulation. Thus antigen-pulsed B cells arrested in the outer PALS in an identical manner irrespective of whether the follicles comprised a population of normal B cells with multiple specificities, a monoclonal naive population, or a monoclonal population of tolerant B cells. In addition, tolerant B cells were found to relocate from the follicles to the outer PALS of HEL/anti-HEL double Tg mice in which the concentration of soluble self-antigen had been increased by zinc feeding. Similarly, when anti-HEL Tg mice were crossed with a second HEL Tg strain expressing a higher concentration of soluble HEL, the tolerant anti-HEL Tg B cells were located constitutively in the outer PALS. Thus, subtle variations in antigen concentration resulted in dramatic changes in positioning of B cells within the spleen. A series of mixed bone marrow chimeras in which the effective antigen concentration was inversely related to the number of self-reactive B cells due to absorption of antigen by transgene-encoded membrane and secreted Ig, was used to confirm that alteration in B cell position previously attributed to changes in follicular composition could be explained on the basis of available antigen concentration, rather than the diversity of the repertoire.

Influences on the lifespan of B cell subpopulations defined by different phenotypes

The turnover of mature and immature B cells defined by a range of cell surface markers was investigated by feeding normal or bcl-2-transgenic (bcl-2-Tg) mice 5'-bromo-2-deoxyuridine (BrdUrd) for up to 6 weeks. In peripheral lymphoid tissue, B cells accumulated BrdUrd with a 50% labeling time of 4.3 weeks and a pattern of uptake indicative of the presence of both long-lived and short-lived cells. These two kinetic populations could be resolved into immature B220lo/heat-stable antigen (HSA)hi cells which labeled rapidly, and B220hiHSAlo cells which were uniformly long-lived with a half-life of about 6 weeks. During loading and pulse-chase experiments, BrdUrd uptake by cells within the mature B220hiHSAlo population clearly followed an exponential kinetic pattern, suggesting that their loss was governed by stochastic processes. Using other surface markers, the long-lived population could also be defined by high expression of IgD, representing cells in the follicular mantle zone of the spleen, and by the phenotype IgMhiIgDloHSAlo which most likely represented marginal zone memory B cells. CD23 expression on B cells did not differentiate well between long and short-lived cells. Only about half of newly labeled B cells appearing in the spleen progressed to the long-lived compartment, a proportion which was not altered significantly in bcl-2-Tg mice. The most likely explanation was that a combination of both positive and negative selection was operating at this site which was mediated by pathways not regulated by bcl-2. On the other hand, overexpression of bcl-2 did result in a two- to threefold increase in the rate of appearance of newly labeled B cells in the spleen, consistent with a possible role for this protein during early selection events within the bone marrow. Selection processes appeared to be very active in young mice during the shaping of the B cell repertoire, since B cells from 6-week-old non-Ig mice displayed a rapid rate of turnover irrespective of their surface phenotype, and a significant population of long-lived cells did not become evident until the mice had reached about 12 weeks of age.

Modeling immunotherapy for allergy

Type I hypersensitivity, which functions to protect the organism from parasites, is caused by binding of antigen to IgE antibodies pre-attached to the cell surface of tissue mast cells and their circulating counterparts, the basophils. In "allergy," type I hypersensitivity is inappropriately induced by protein-based foreign substances (such as pollen) or protein components of insect stings, which in the normal course of events would be cleared from the organism without causing any damage. Paradoxically, a successful clinical treatment of allergy involves repeated immunization of allergic persons with low doses of the allergen--immunotherapy. Investigation of the available experimental evidence leads to the conclusion that the phenomena of immunotherapy are best addressed in terms of the interplay among the mechanism(s) of immune memory--Th1/Th2 cross-regulation--and the physical compartmentalization of the immune system. These conclusions are illustrated with a numerical simulation.

Peritoneal defences and peritoneum-associated lymphoid tissue

The peritoneum is mainly protected by the innate immune system. This consists of mechanical clearance of the peritoneal cavity, activation of complement, and the actions of polymorphonuclear neutrophils and macrophages. The specific immune system, which is mediated by the activity of lymphocytes, provides a secondary amplification system that may be of great importance for patients with intraperitoneal sepsis. This review provides an overview of the relevant innate immune mechanisms and explores the possible role of peritoneum-associated lymphoid tissue.

Continuous ambulatory peritoneal dialysis impairs T lymphocyte selection in the peritoneum

Peritoneal lymphocytes (PCL) of 45 healthy individuals, four uremic patients with end-stage renal disease (ESRD) and 25 long-term continuous ambulatory peritoneal dialysis (CAPD) patients were characterized by flow cytometry to investigate whether CAPD alters the phenotype of PCL. B lineage cells constitute a minority of PCL (2.5% of cells). Although the majority of peritoneal T cells expressed alpha beta T cell receptor (TcR), 7% expressed gamma delta TcR, a proportion which was significantly higher than that in peripheral blood (PBMC) (approximately 4%). The majority of PCL T cells exhibited markers of the thymus-dependent lineage (CD2, CD3, TcR alpha beta, CD8 alpha beta or CD4) and surface antigens associated with memory and activation (CD45RO, CD11a, CD18, CD49d, HLA-DR). An average of 75% of both CD4+ and CD8+ PCL T cells of healthy subjects and CAPD patients were CDw60+, thus characterizing the T cell subset containing the helper activity for the mitogen-driven B cell differentiation. CD44s was abundantly expressed on PCL T cells. In contrast to PCL T cells of healthy subjects peritoneal T lymphocytes of CAPD patients exhibited CD44 splice variants containing products of exon-v9 and the proportion of CD44v9+ cells correlated with the frequency of peritonitis episodes the patients had gone through. The majority of PCL T cells of both healthy subjects and CAPD patients were CD8+. A large proportion of CD8+ PCL T cells from healthy subjects expressed the homodimeric CD8 alpha alpha isoform; however, such cells were not found in CAPD patients. In healthy subjects mRNA for the recombination activating gene 1 (RAG-1) was detectable in a PCL population containing CD7-CD34+ and CD7+CD34+ cells. In contrast, neither mRNA transcripts of the RAG-1 gene nor CD34+ cells were detectable in PCL of CAPD patients.

T lymphocytes from the normal human peritoneum contain high frequencies of Th2-type CD8+ T cells

The majority of peritoneal T lymphocytes have been shown to be CD8+ and to co-express CDw60. Expression of CDw60 characterizes CD8 T cells capable of secreting interleukin (IL)-4 and supporting IgG production by B cells. We analyzed at the clonal level the functional cytokine profile of CD8+ T lymphocytes from the normal human peritoneum. While the majority of the clones produced interferon (IFN)-gamma and exhibited high alloantigen-specific cytolytic activity, some clones secreted IL-4 and IL-5 but no detectable IFN-gamma. These Th2-type CD8+ T cell clones provided substantial B cell help for IgG and IgA synthesis and exhibited reduced cytolytic activity. Our results suggest that distinct subsets of CD8+ T cell may occur in different immune compartments.

Histopathology and immunocytochemical study of type 3 and type 4 complement receptors in the liver and spleen of dogs naturally and experimentally infected with Leishmania (Leishmania) chagasi

The objective of this study was to compare the histopathological changes and expression of CR3 and CR4 in the liver and spleen of dogs naturally and experimentally infected with L. chagasi. The basic histopathological lesions observed mainly in naturally infected dogs were: epithelioid hepatic granulomas, hyperplasia and hypertrophy of Kupffer cells, Malpigui follicles and mononucleated cells of the red pulp of the spleen. Sections from the liver and spleen by immunocytochemistry technique showed the presence of CD11b, c/CD 18 antigens in the control and infected animals and no qualitative or quantitative differences in the liver. Nevertheless, CD18 was always increased in the spleen of naturally and experimentally infected dogs. These results indicate that there is a difference in the activation of CD18 in both experimental and natural cases of canine visceral leishmaniasis that should play an important role in the immunological response to Leishmania chagasi infection.

Dysregulated cytokine expression in vivo in prediseased and diseased autoimmune-prone MRL mice

Macrophages (mø) from prediseased autoimmune-prone MRL/ + and MRL/lpr mice produce markedly decreased levels of IL-1 in vitro in response to LPS. In contrast, tissues from diseased MRL/lpr mice overexpress IL-1 in vivo. To determine whether IL-1 underproduction in the MRL strains is solely an in vitro phenomenon, we compared in vivo cytokine mRNA expression from prediseased age-matched MRL/ + and MRL/lpr mice to that from normal BALB/c and C3HeB/FeJ mice. Like mø in vitro, whole organ RNA from the spleen, liver, and kidney of MRL/ + and MRL/lpr mice showed down-regulation of IL-1 RNA following intraperitoneal injection of LPS. This abnormality in inducible IL-1 expression was present in all MRL mice, irrespective of disease stage or the presence of the lpr gene. On the other hand, only diseased MRL/lpr mice displayed elevated and constitutive expression of IL-1 in their livers and kidneys. We suggest that inducible expression is most indicative of the intrinsic, or genetic, capacity of cells to produce cytokine, whereas constitutive expression reflects extracellular disease-related inflammatory stimuli present only in the diseased MRL/lpr strains. By restricting our studies to prediseased MRL mice, we have tried to eliminate the effects of disease and to focus on the predisposing genetic background. The existence both in vitro and in vivo of a defect in inducible IL-1 expression by prediseased MRL mice suggests that the molecular abnormality underlying this defect may be a part of this predisposing background to autoimmunity.

Parasite-host relationships: in-situ study of Leishmania spp. in resistant and susceptible mice

The host's skin is a critical tissue in the natural life cycle of the Leishmania spp. known to cause an 'asymptomatic' infectious process or cutaneous or visceral leishmaniasis in mammals. The dermis, once disturbed by the inoculation of infective parasites, becomes a site of dynamic events, the progression of which depends upon both host and parasite characteristics. Whatever the final site of the morbidity caused by the parasites, whether it be cutaneous, visceral or muco-cutanous, this site reflects the parasite and host's ability to create a pro- or anti-parasite micro-environment. The characteristics of this environment are now amenable to analysis in situ, as illustrated by the study of the cutaneous processes initiated by inoculation of Leishmania major in laboratory mice.

T lymphocytes from normal human peritoneum are phenotypically different from their counterparts in peripheral blood and CD3- lymphocyte subsets contain mRNA for the recombination activating gene RAG-1

The surface antigens of peritoneal lymphocytes of healthy human individuals were studied. B lineage cells comprised 2.3% of the total peritoneal lymphocyte population. Although the majority of peritoneal cavity lymphocyte (PCL) T cells expressed alpha beta T cell receptor (TcR), up to 17% expressed gamma delta TcR. The majority of PCL exhibited markers of the thymus-dependent lineage (CD2+ CD3+ TcR alpha beta + CD4+ or CD8 alpha + beta +) and surface antigens associated with memory and activation (CD45RO+ CD11a+ CD18+ CD49d+ HLA-DR). Up to 92% of both CD4+ and CD8+ T cells bore CDw60, thus characterizing the T cell subset containing helper activity for mitogen-driven B cell differentiation. The majority of PCL T cells were CD8+ and, in addition, up to 60% of this population expressed the homodimeric CD8 alpha + beta -. Messenger RNA for the recombination activating gene RAG-1 was examined in CD3- PCL depleted of CD19+ lineage cells. The PCL population which comprised cells containing RAG-1 mRNA transcripts was CD19-, surface IgM-, cytoplasmic IgM- and CD2- CD3- CD4- CD8- CD56-. However, this population was CD7+ (approx. 75%), and contained both CD7- CD34+ (up to 3%) and CD7- CD34+ (up to 3%) cells. These findings are compatible with the hypothesis that the adult human peritoneum provides a microenvironment capable of supporting a thymus-indenpendent differentiation of T lymphocytes.

Biochemical and phenotypic characterization of the ovine beta 2 (leucocyte) integrins

This paper is concerned with the relationship of the three distinct members of the ovine beta 2-integrin family of leucocyte adhesion molecules that play an important role in cell-cell and cell-matrix interactions. A panel of monoclonal antibodies (mAbs) specific for sheep and cattle macrophages was characterized by flow cytometry, immunohistology, and immunoprecipitation for reactivity to the beta 2 integrins. Immunoprecipitation analysis of sheep antigens showed that these monoclonal antibodies could be divided into four distinct groups. All precipitated an M(r) 95,000 beta chain but they differed in the size or number (or both) of the alpha chains recognized. Group 1 precipitated alpha chains of M(r) 180,000; group 2 had M(r) 170,000 alpha chains; the group 3 alpha chain was of M(r) 150,000 and group 4 mAbs precipitated alpha chains of all three sizes. The relationship between these antibodies was demonstrated by sequential immunoprecipitation, which showed that the reactivities of antibodies in groups 1, 2 and 3 were mutually exclusive but that group 4 antibodies shared a common specificity with the other three groups. By analogy with the human and murine beta 2 integrin families, group 1 antibodies seemed to be specific for CD11a (LFA-1); group 2 were CD11b (CR3 or Mac1); group 3 were CD11c (CR4 or p150/95) and group 4 were CD18. In addition to different molecular weights, these antibodies had different cellular and tissue distributions. CD11a and CD18 were distributed identically. The antigens recognized by both were present on all the leucocyte populations. The mAbs recognizing CD11b reacted with a sub-population of peripheral blood B lymphocytes and all myeloid cells (alveolar macrophages, peripheral blood monocytes and granulocytes) except afferent lymph dendritic cells (ADC). Anti-CD11c (p 150/95 or CR4) antibodies reacted strongly with macrophages and ADC but were weakly reactive on monocytes and negative on neutrophils. CD11c was also present on a sub-population of peripheral blood B cells.

The regulation of pulmonary immunity

No evidence has emerged which suggests that the principles of immunity derived from studies on cells from other body sites are contradicted in the lung and its associated lymphoid tissue. What is clear, however, is that the environment dictates the types of cells, their relationship to one another, and what perturbing events will set in motion either the development of an "active" immune response or tolerance. Investigating mechanisms for the development of lung immunity has increased our understanding of how human diseases develop and is continuing to suggest new ways to manipulate pulmonary immune responses. Demonstration that lung cells regulate both nonspecific inflammation and immunity through the expression of adhesion molecules and the secretion of cytokines offers hope for ways to design more effective vaccines, enhance microbial clearance in immunosuppressed hosts, and to suppress manifestations of immunologically mediated lung disease. Important lung diseases targeted for intensive research efforts in the immediate future are tuberculosis, asthma, and fibrotic lung disease. Perhaps even the common cold might be conquered. Considering the pace of current research on lung immunity, it may not be too ambitious to predict that these diseases may be conquered in the next decade.

Transient inducible events in different tissues: in situ studies in the context of the development and expression of the immune responses to intracellular pathogens

Intracellular pathogens whether facultative like Mycobacterium sp., e.g. Bacillus Calmette Guérin, Listeria monocytogenes or strictly intracellular like Leishmania sp. initiate either asymptomatic infectious processes or disease depending both on factors of the host (genetic as well as environmental ones) and the infectious/pathogenic agents. In this contribution, we first summarized informations which justify to develop in situ analysis to decipher the sequential events that result in different modes/classes of immune responses. How the mode of the immune response is determined remains a main question to address. Although it has recently become clear, in vitro, that immunocompetent cells and their cytokines are critical to set on a stable mode of immune response, acting on naive T cells, this area deserves more in vivo studies. Indeed, peripheral T cells, at different stages of differentiation, may exist in vivo (a) naive/virgin, (b) experienced, (c) effector T cells, depending on the level of stimulation of the immune system by either endogenous or exogenous (e.g. gut flora) signals. The three chosen examples illustrate our contributions in this field focusing on three different non-lymphoid tissues which may become infected: bone marrow (Bacille de Calmette Guérin), liver (Listeria monocytogenes), skin (Leishmania major). These three illustrations also allow to attract attention on the interest of using mice of genetically different strains the immune response of which is set up under different modes.

FACS analysis of peritoneal lymphocytes in ovarian cancer and control patients

In this study different lymphocyte populations in the malignant ascites of 10 patients with ovarian carcinoma and in the peritoneal fluid of 8 control patients (tubal ligation and benign conditions) were analyzed. A panel of monoclonal antibodies against the CD markers of lymphocytes was used to stain different populations and the cells were analyzed on a FACS II (fluorescence-activated cell sorter). The mean percentage of B lymphocytes in the peritoneal cavity of the OVCA patients was 0.18 +/- 0.5% and in the control patients 0.05 +/- 0.07%. There was no significant difference between the two groups. In the OVCA group and in the controls the percentage of T lymphocytes (CD5+) was 23.5% and 17.1% respectively with no significant difference between the groups. These results indicate that B lymphocytes are not present in the human peritoneal cavity. The small numbers of B cells found in this study could be due to contamination with peripheral blood. The human peritoneal cavity contains a cell population which differs from that present in peripheral blood. Significant numbers of B lymphocytes have been reported in the peritoneal cavity of mice. The difference between the lymphocyte population of the human peritoneal cavity and that of rodents implies that data on characterization and function of B lymphocytes in the mouse peritoneal cavity would not be applicable to humans.