Coexpression of type 2 immune targets in sputum-derived epithelial and dendritic cells from asthmatic subjects

BACKGROUND

Noninvasive sputum sampling has enabled the identification of biomarkers in asthmatic patients. Studies of discrete cell populations in sputum can enhance measurements compared with whole sputum in which changes in rare cells and cell-cell interactions can be masked.

OBJECTIVE

We sought to enrich for sputum-derived human bronchial epithelial cells (sHBECs) and sputum-derived myeloid type 1 dendritic cells (sDCs) to describe transcriptional coexpression of targets associated with a type 2 immune response.

METHODS

A case-control study was conducted with patients with mild asthma (asthmatic cases) and healthy control subjects. Induced sputum was obtained for simultaneous enrichment of sHBECs and sDCs by using flow cytometry. Quantitative PCR was used to measure mRNA for sHBEC thymic stromal lymphopoietin (TSLP), IL33, POSTN, and IL25 and downstream targets in sDCs (OX40 ligand [OX40L], CCL17, PPP1R14A, CD1E, CD1b, CD80, and CD86).

RESULTS

Final analyses for the study sample were based on 11 control subjects and 13 asthmatic cases. Expression of TSLP, IL33, and POSTN mRNA was increased in sHBECs in asthmatic cases (P = .001, P = .05, and P = .04, respectively). Expression of sDC OX40L and CCL17 mRNA was increased in asthmatic cases (P = .003 and P = .0001, respectively). sHBEC TSLP mRNA expression was strongly associated with sDC OX40L mRNA expression (R = 0.65, P = .001) and less strongly with sDC CCL17 mRNA expression. sHBEC IL33 mRNA expression was associated with sDC OX40L mRNA expression (R = 0.42, P = .04) but not sDC CCL17 mRNA expression.

CONCLUSIONS

Noninvasive sampling and enrichment of select cell populations from sputum can further our understanding of cell-cell interactions in asthmatic patients with the potential to enhance endotyping of asthmatic patients.

Co-ordinate expression of Th1/Th2 phenotypes in maternal and fetal blood: evidence for a transplacental nexus

If maternal atopy and environmental exposure affect prenatal Th cell development, the maternal and fetal immune systems should display common Th1/Th2 phenotypes. To test this hypothesis, we studied maternal and neonatal blood samples from mothers with total serum IgE <300 IU/mL. Basal levels of IFN-γ, IL-4, and eotaxin in paired maternal and fetal sera were tightly correlated. Polyclonal T cell activation in vitro by Staphylococcal exotoxin B induced co-ordinate IFN-γ production from paired maternal and fetal mononuclear cells, accompanied by co-ordinate increases in activated CD4+CD69+ cells that display the CCR4+Th2 and CXCR3+ Th1 phenotypes. Maternal and fetal CD4+CXCR3+ T cells were subsequently identified as the major producers of IFN-γ. The data established that a transplacental nexus exists during normal pregnancy and that fetal Th cell responses may be biased by the maternal immune system.

Improving immunogenicity of HIV-1 envelope gp120 by glycan removal and immune complex formation

HIV-1 envelope (Env) gp120 is an important target for neutralizing antibody (Ab) responses against the virus; however, developing gp120 vaccines that elicit potent and broad neutralizing Abs has proven to be a formidable challenge. Previously, removal of an N-linked glycan at residue 448 by an N to Q mutation (N448Q) has been found to enhance the in vitro antigenicity of neutralizing epitopes in the V3 loop. In this study the mutated gp120 was first compared with wild type gp120 for immunogenicity in mice using a DNA prime and protein boost immunization regimen. The N448Q mutant did not elicit higher titers of anti-gp120 serum Abs and failed to generate anti-V3 Abs. The sera also had no virus-neutralizing activity, even though the mutant induced higher levels of lymphoproliferation and cytokine production. Subsequently, the N448Q mutant was used to construct an immune complex vaccine with the anti-CD4 binding site monoclonal antibody (mAb) 654. The N448Q/654 complex stimulated comparably high levels of serum Abs to gp120 and V3 as the wild type complex. However, Abs against the C1 and C2 regions in the gp120 core were more elevated. Importantly, the mutant complex also elicited higher titers of neutralizing Abs activity than the wild type counterpart. Similar results were achieved with a complex made with gp120 bearing an N448E mutation, confirming the importance of the N448-linked glycan in modulating gp120 immunogenicity. Neutralizing activity was directed to V3 and other undefined neutralizing epitopes. Improved immunogenicity of the immune complexes correlated with alterations in exposure of V3 and other Ab epitopes and their stability against proteases. These data demonstrate the advantage of combining site-specific N-glycan removal and immune complex formation as a novel vaccine strategy to improve immunogenicity of targeted Ab epitopes on critical regions of HIV-1 gp120.

Cytokine responses to QuantiFERON® peptides, purified protein derivative and recombinant ESAT-6 in children with tuberculosis

SETTING

Recent data suggest that interferon-gamma release assays may have reduced sensitivity in children.

OBJECTIVE

To explore the cellular responses in children infected with tuberculosis (TB) to different mycobacterial antigens, including the peptides used in the QuantiFERON®-TB Gold In-Tube (QFT) assay.

DESIGN

Cytokines were measured by multiplex analyte detection in supernatants after stimulation with peptides in QFT, purified protein derivative (PPD) and recombinant whole protein ESAT-6. Samples from 11 children with active TB, 46 healthy children with latent tuberculosis infection (LTBI), and 35 healthy non-infected children were analyzed.

RESULTS

None of the cytokines examined in the QFT peptide stimulation assay distinguished between non-infected children and those aged <5 years with LTBI. Cytokines interleukin-2 and transforming growth factor-beta 1 (TGF-β1) were shown to distinguish between stages of Mycobacterium tuberculosis infection after blood was stimulated with the QFT peptides. All children had significantly higher Th 1 and 2 cytokine production against PPD than against the other antigens tested.

CONCLUSION

Measuring specific cytokine patterns after stimulation with the QFT peptides may not increase sensitivity in diagnosing LTBI in children, but there may be future diagnostic value in determining the stage of infection. PPD-stimulated blood produced a robust and diverse cytokine response in young children, making it an interesting antigen for in vitro diagnostic studies.

Diesel exhaust particle-treated human bronchial epithelial cells upregulate Jagged-1 and OX40 ligand in myeloid dendritic cells via thymic stromal lymphopoietin

Ambient particulate matter, including diesel exhaust particles (DEP), promotes the development of allergic disorders. DEP increase oxidative stress and influence human bronchial epithelial cell (HBEC)-dendritic cell interactions via cytokines, including thymic stromal lymphopoietin (TSLP). Upregulation of TSLP results in Th2 responses. Using primary culture HBEC and human myeloid dendritic cell (mDC) cocultures, we show in this study that DEP upregulation of Th2 responses occurred via HBEC-dependent mechanisms that resulted from oxidative stress. Moreover, DEP-treated HBEC and ambient particulate matter-treated HBEC upregulated OX40 ligand (OX40L) and the Notch ligand Jagged-1 mRNA and expression on mDC. Upregulation of OX40L as well as Jagged-1 on mDC required HBEC and did not occur in the presence of N-acetylcysteine. Furthermore, OX40L and Jagged-1 upregulation was inhibited when HBEC expression of TSLP was silenced. Thus, DEP treatment of HBEC targeted two distinct pathways in mDC that were downstream of TSLP expression. Upregulation of OX40L and Jagged-1 by mDC resulted in mDC-driven Th2 responses. These studies expand our understanding of the mechanism by which ambient pollutants alter mucosal immunity and promote disorders such as asthma.

Host-dependent Lewis (Le) antigen expression in Helicobacter pylori cells recovered from Leb-transgenic mice

Variation of surface antigen expression is a mechanism used by microbes to adapt to and persist within their host habitats. Helicobacter pylori, a persistent bacterial colonizer of the human stomach, can alter its surface Lewis (Le) antigen expression. We examined H. pylori colonization in mice to test the hypothesis that host phenotype selects for H. pylori (Le) phenotypes. When wild-type and Le^b-expressing transgenic FVB/N mice were challenged with H. pylori strain HP1, expressing Le^x and Le^y, we found that bacterial populations recovered after 8 mo from Le^b-transgenic, but not wild-type, mice expressed Le^b. Changes in Le phenotype were linked to variation of a putative galactosyltransferase gene (β-(1,3)galT); mutagenesis and complementation revealed its essential role in type I antigen expression. These studies indicate that H. pylori evolves to resemble the host's gastric Le phenotype, and reveal a bacterial genetic locus that is subject to host-driven selection pressure.

Hyper interleukin-10 in an HIV-positive child with t-cell lymphoma and candidal sepsis

We describe a case in which a human immunodeficiency virus (HIV)-positive child presented in severe metabolic acidosis secondary to his candidal sepsis and T-cell lymphoma, a rare finding in pediatric AIDS. Significantly elevated levels of Interleukin-10 (IL-10) were found in the patient's serum, which may have played a role in acute demise.

CCR5 expression and duration of high risk sexual activity among HIV-seronegative men who have sex with men

OBJECTIVES

To test the hypothesis that in comparison with those with shorter risk duration, individuals with longer HIV risk duration would have reduced susceptibility to HIV-1 infection as measured by CCR5 expression, and to evaluate whether variation in CCR5 expression could be explained by known genetic polymorphisms.

DESIGN AND METHODS

A cross-sectional study of HIV-1 exposed but uninfected men who have sex with men. The risk duration was estimated from self-reported years since first receptive anal intercourse. CCR5 expression on peripheral blood CD4+ monocytes and T cells was determined by flow cytometry. The CCR5-Delta32 mutation and polymorphisms in the CCR5 promoter and CCR2 as well as the copy number of CCL3L1 were analyzed by polymerase chain reaction. Plasma levels of MIP-1alpha (CCL3), MIP-1beta (CCL4) and RANTES (CCL5) were also measured. As risk duration varied with age, analyses were restricted to 67 individuals aged 30-49 years.

RESULTS

Multiple linear regression analyses, adjusted for age and race, showed a significant negative association between HIV risk duration and CCR5 expression on monocytes (P = 0.01), and in a separate model, a similar negative association with CCR5 expression on T cells (P = 0.03). Low CCR5 expression was attributable mainly to CCR5-Delta32 heterozygosity and the CCR5-59029G allele.

CONCLUSIONS

We confirmed a role for reduced CCR5 expression in HIV-1 resistance. CCR5-Delta32 heterozygosity and the CCR5-59029G allele were significant predictors of low CCR5 expression. Individuals with high CCR5 expression who resisted infection despite long HIV risk duration form an interesting group within which to search for additional mechanisms of resistance to HIV infection.

Diesel exhaust particle-exposed human bronchial epithelial cells induce dendritic cell maturation

Increased exposure to air pollutants such as diesel exhaust particles (DEP) has been proposed as one mechanism to explain the rise in allergic disorders. However, the immunologic mechanisms by which DEP enhance allergic sensitization and asthma remain unclear. We hypothesized that DEP act as an adjuvant for immature dendritic cell (DC) maturation via its effect on airway epithelial cell-derived microenvironment for DC. Immature monocyte-derived DC (iMDDC) failed to undergo phenotypic (CD80, CD83, CD86) or functional (T cell activation) maturation in response to exposure to DEP (0.001-100 mug/ml). In contrast, primary cultures of human bronchial epithelial cells (HBEC) treated with DEP induced iMDDC phenotypic maturation (2.6 +/- 0.1-fold increase in CD83 expression, n = 4, p < 0.05) and functional maturation (2.6 +/- 0.2-fold increase in T cell activation, n = 4, p < 0.05). Functional maturation of iMDDC was induced by conditioned medium derived from DEP-treated HBEC, and was inhibited in cultures with DEP-treated HBEC and blocking Abs against GM-CSF, or GM-CSF-targeted small interfering RNA. These data suggest that DEP induce Ag-independent DC maturation via epithelial cell-DC interactions mediated by HBEC-derived GM-CSF. Although additional signals may be required for polarization of DC, these data suggest a novel mechanism by which environmental pollutants alter airway immune responses.

Heterogeneity in fetal immunocompetence during the second trimester of gestation. Implications for treatment of nonimmune genetic disorders by in utero transplantation

OBJECTIVE

To address the role that alloreactivity may play and better define the window for histoincompatible stem cell transplantation in utero.

SUBJECTS, MATERIAL AND METHODS

We studied 9 fetal blood specimens obtained by cardiocentesis during elective abortions in the second trimester by multicolor flow cytometry and in vitro stimulation.

RESULTS

Lymphocytes ranged from adult levels (3/9) to >90% leukocytes. Six specimens had T cells within adult range. T cells in the other specimens were reduced, while B cells were conversely elevated. This variability did not correlate with gestational age, or leukocyte composition. Following 4 h of mitogenesis, fetal CD4+ and CD8+ T cells from 1 of 5 specimens showed a response similar to that of maternal T cells, while the other 4 specimens showed a diminished response (0.3 +/- 0.2-fold). This heterogeneity did not correlate with gestational age, or lymphocyte subset distribution. Following 18 h of in vitro mitogenesis, fetal T cells from 2 specimens showed a response similar to that of maternal T cells (0.8 +/- 0.2-fold). Despite that, one specimen gave a 3-fold greater response in a one-way mixed lymphocyte reaction vs. maternal cells compared to the other specimen.

CONCLUSION

We determine that fetal immunocompetence differs greatly during the second trimester and assessment of host vs. donor reactivity prior to in utero transplantation is likely to potentiate more favorable outcomes.

IFN-αβ Secreted during Infection Is Necessary but Not Sufficient for Negative Feedback Regulation of IFN-αβ Signaling byMycobacterium tuberculosis

IFN-alphabeta functions in the transition from innate to adaptive immunity and may impinge on the interaction of Mycobacterium tuberculosis with its host. Infection by M. tuberculosis causes IFN-alphabeta secretion and down-regulation of IFN-alphabeta signaling in human APC and the human monocytic cell line THP-1, which provides a model for these studies. Neutralization of secreted IFN-alphabeta prevents inhibition of IFN-alpha signaling during infection, but several lines of evidence distinguish inhibition due to infection from a negative feedback response to only IFN-alphabeta. First, greater inhibition of IFN-alpha-stimulated STAT-1 tyrosine phosphorylation occurs 3 days postinfection than 1 or 3 days after IFN-alphabeta pretreatment. Second, LPS also induces IFN-alphabeta secretion and causes IFN-alphabeta-dependent down-regulation of IFN-alpha signaling, yet the inhibition differs from that caused by infection. Third, IFN-alpha signaling is inhibited when cells are grown in conditioned medium collected from infected cells 1 day postinfection, but not if it is collected 3 days postinfection. Because IFN-alphabeta is stable, the results with conditioned medium suggest the involvement of an additional, labile substance during infection. Further characterizing signaling for effects of infection, we found that cell surface IFN-alphabeta receptor is not reduced by infection, but that infection increases association of protein tyrosine phosphatase 1c with the receptor and with tyrosine kinase 2. Concomitantly, IFN-alpha stimulation of tyrosine kinase 2 tyrosine phosphorylation and kinase activity decreases in infected cells. Moreover, infection reduces the abundance of JAK-1 and tyrosine-phosphorylated JAK-1. Thus, the distinctive down-regulation of IFN-alpha signaling by M. tuberculosis occurs together with a previously undescribed combination of inhibitory intracellular events.

Mycobacterium tuberculosis-induced CXCR4 and chemokine expression leads to preferential X4 HIV-1 replication in human macrophages

Opportunistic infections such as pulmonary tuberculosis (TB) increase local HIV-1 replication and mutation. As AIDS progresses, alteration of the HIV-1 gp120 V3 sequence is associated with a shift in viral coreceptor use from CCR5 (CD195) to CXCR4 (CD184). To better understand the effect of HIV/TB coinfection, we screened transcripts from bronchoalveolar lavage cells with high density cDNA arrays and found that CXCR4 mRNA is increased in patients with TB. Surprisingly, CXCR4 was predominately expressed on alveolar macrophages (AM). Mycobacterium tuberculosis infection of macrophages in vitro increased CXCR4 surface expression, whereas amelioration of disease reduced CXCR4 expression in vivo. Bronchoalveolar lavage fluid from TB patients had elevated levels of CCL4 (macrophage inflammatory protein-1beta), CCL5 (RANTES), and CX3CL1 (fractalkine), but not CXCL12 (stromal-derived factor-1alpha). We found that M. tuberculosis infection of macrophages in vitro increased viral entry and RT of CXCR4-using [corrected] HIV-1, but not of CCR5-using [corrected] HIV-1. Lastly, HIV-1 derived from the lung contains CD14, suggesting that they were produced in AM. Our results demonstrate that TB produces a permissive environment for replication of CXCR4-using virus by increasing CXCR4 expression in AM and for suppression of CCR5-using HIV-1 by increasing CC chemokine expression. These changes explain in part why TB accelerates the course of AIDS. CXCR4 inhibitors are a rational therapeutic approach in HIV/TB coinfection.

CD40 contributes to lethality in acute sepsis: in vivo role for CD40 in innate immunity

Sepsis induces an early inflammatory cascade initiated by the innate immune response. This often results in the development of multisystem organ failure. We examined the role of CD40, a costimulatory molecule that is integral in adaptive immunity, by using a murine model of polymicrobial sepsis. CD40 knockout (KO) mice had delayed death and improved survival after cecal ligation and puncture (CLP). In addition, they had less remote organ injury as manifested by reduced pulmonary capillary leakage. The improvements in survival and remote organ dysfunction in CD40 KO mice were associated with reduced interleukin-6 (IL-6) and IL-10 levels in serum and bronchoalveolar lavage fluid compared to the levels in wild-type (WT) controls. Furthermore, in contrast to WT mice, CD40 KO mice had no induction of the Th1 cytokines IL-12 and gamma interferon in serum or lungs after CLP. The alterations in cytokine production in CD40 KO mice were associated with similar changes in transcription factor activity. After CLP, CD40 KO mice had attenuated activation of nuclear factor kappaB and signal transducer and activator of transcription 3 in both the lung and the liver. Finally, WT mice had increased expression of CD40 on their alveolar macrophages. These data highlight the importance of CD40 activation in the innate immune response during polymicrobial sepsis and the subsequent development of remote organ dysfunction.

Acute eosinophilic pneumonia in a New York City firefighter exposed to World Trade Center dust

We report a sentinel case of acute eosinophilic pneumonia in a firefighter exposed to high concentrations of World Trade Center dust during the rescue effort from September 11 to 24. The firefighter presented with a Pa(O2) of 53 mm Hg and responded to oxygen and corticosteroids. Computed tomography scan showed patchy ground glass density, thickened bronchial walls, and bilateral pleural effusions. Bronchoalveolar lavage recovered 70% eosinophils, with only 1% eosinophils in peripheral blood. Eosinophils were not degranulated and increased levels of interleukin-5 were measured in bronchoalveolar lavage and serum. Mineralogic analysis counted 305 commercial asbestos fibers/10(6) macrophages including those with high aspect ratios, and significant quantities of fly ash and degraded fibrous glass. Acute eosinophilic pneumonia is a rare consequence of acute high dust exposure. World Trade Center dust consists of large particle-size silicates, but fly ash and asbestos fibers may be found in bronchoalveolar lavage cells.

Maximal HIV-1 replication in alveolar macrophages during tuberculosis requires both lymphocyte contact and cytokines

HIV-1 replication is markedly upregulated in alveolar macrophages (AM) during pulmonary tuberculosis (TB). This is associated with loss of an inhibitory CCAAT enhancer binding protein beta (C/EBPbeta) transcription factor and activation of nuclear factor (NF)-kappaB. Since the cellular immune response in pulmonary TB requires lymphocyte--macrophage interaction, a model system was developed in which lymphocytes were added to AM. Contact between lymphocytes and AM reduced inhibitory C/EBPbeta, activated NF-kappaB, and enhanced HIV-1 replication. If contact between lymphocytes and macrophages was prevented, inhibitory C/EBPbeta expression was maintained and the HIV-1 long terminal repeat (LTR) was not maximally stimulated although NF-kappaB was activated. Antibodies that cross-linked macrophage expressed B-7, and vascular cell adhesion molecule and CD40 were used to mimic lymphocyte contact. All three cross-linking antibodies were required to abolish inhibitory C/EBPbeta expression. However, the HIV-1 LTR was not maximally stimulated and NF-kappaB was not activated. Maximal HIV-1--LTR stimulation required both lymphocyte-derived soluble factors, and cross-linking of macrophage expressed costimulatory molecules. High level HIV-1--LTR stimulation was also achieved when IL-1beta, IL-6, and TNF-beta were added to macrophages with cross-linked costimulatory molecules. Contact between activated lymphocytes and macrophages is necessary to down-regulate inhibitory C/EBPbeta, thereby derepressing the HIV-1 LTR. Lymphocyte-derived cytokines activate NF-kappaB, further enhancing the HIV-1 LTR.

In situ activation of helper T cells in the lung

To better understand the lung and systemic responses of helper T cells mediating memory immunity to Mycobacterium tuberculosis, we used three- and four-color flow cytometry to study the surface phenotype of CD4(+) lymphocytes. Bronchoalveolar lavage (BAL) fluid and peripheral blood (PB) samples were obtained from a total of 25 subjects, including 10 tuberculosis (TB)-infected subjects, 8 purified-protein-derivative-negative subjects, and 7 purified-protein-derivative-positive subjects. In marked contrast to CD4(+) lymphocytes from PB (9% +/- 5% expressing CD45RA and CD29), the majority (55% +/- 16%) of CD4(+) lymphocytes in BAL (ALs) simultaneously expressed CD45RA, a naïve T-cell marker, and CD29, members of the very late activation family. Further evaluation revealed that CD4(+) ALs expressed both CD45RA and CD45RO, a memory T-cell marker. In addition, the proportion of CD4(+) lymphocytes expressing CD69, an early activation marker, was drastically increased in BAL fluid (83% +/- 9%) compared to PB (1% +/- 1%), whereas no significant difference was seen in the expression of CD25, the low-affinity interleukin 2 receptor (34% +/- 15% versus 40% +/- 16%). More importantly, we identified a minor population of CD69(bright) CD25(bright) CD4(+) lymphocytes in BAL (10% +/- 6%) that were consistently absent from PB (1% +/- 1%). Thus, CD4(+) lymphocytes in the lung paradoxically coexpress surface molecules characteristic of naïve and memory helper T cells as well as surface molecules commonly associated with early and late stages of activation. No difference was observed for ALs obtained from TB-infected and uninfected lung segments in this regard. It remains to be determined if these surface molecules are induced by the alveolar environment or if CD4(+) lymphocytes coexpressing this unusual combination of surface molecules are selectively recruited from the circulation. Our data suggest that ex vivo experiments on helper T-cell subsets that display distinctive phenotypes may be pivotal to studies on the human immune response to potential TB vaccines.

Effect of CD4 engagement on CD4-T cell receptor complexes

To detect the presence of CD4-T cell receptor (TCR) complexes, we previously developed a flow cytometric method for measuring singlet-singlet energy transfer on human T cells labeled with fluorescein isothiocyanate-conjugated anti-CD4 and tetramethylrhodamine isothiocyanate-conjugated anti-TCR. Using the same procedure, we have now studied changes in the expression of CD4, TCR, and CD4-TCR complexes following CD4 engagement. Ligation of the D3 domain with OKT4, or the D1 domain with anti-Leu3a, induced CD4 and TCR down-regulation, while ligation of the D1 domain with gp120 did not. OKT4 caused a transient decrease in CD4-TCR association over 1 hr at 37 degrees C, while anti-Leu3a caused a steady-state decrease. In contrast, gp120 decreased CD4-TCR association mainly at 0 degrees C, rather than at 37 degrees C. Such alteration in CD4-TCR assembly may underly anti-Leu3a- and gp120-mediated inhibition of T cell antigen recognition and account for the negative effect of CD4 ligation on TCR-triggered responses.

Architectural organization in the interphase nucleus of the protozoan Trypanosoma brucei: location of telomeres and mini-chromosomes

We studied the spatial organization of chromatin in the interphase G1, S and G2 nucleus of the protozoan Trypanosoma brucei, applying in situ hybridization with conventional fluorescence and confocal scanning optical microscopy. The majority of the trypanosome telomere GGGTTA repeats from different chromosomes were found clustered together, either extending in a network through the nuclear interior or localized at the nuclear periphery. The population of one hundred mini-chromosomes was often asymmetrically located: either clustered in a narrow band in close association with the nuclear envelope or distributed into several clusters that segregated into roughly one half of the nucleus. The nuclear organization may undergo modifications during the cell cycle and development. We conclude that non-random spatial positioning of DNA exists in the nucleus of this protozoan. Finding a high level of structural organization in the interphase nucleus of T.brucei is an important first step towards understanding chromosome structure and functioning and its role in the control of gene expression.

CD4-T-cell antigen receptor complexes on human leukemia T cells

CD4 and T-cell antigen receptor (TCR) comodulate from the surface of human and murine T cells following exposure to monoclonal anti-CD4 or anti-TCR. This comodulation may occur because expression of CD4 and TCR is regulated by similar transmembrane signals or because CD4 and TCR are physically associated. To study multimolecular assemblies on the plasma membrane, we developed a flow cytometric method for detecting singlet-singlet energy transfer between fluorescein isothiocyanate (FITC)- and tetramethylrhodamine isothiocyanate (TRITC)-conjugated monoclonal antibodies as sensitized TRITC emission on intact, single cells. Using this procedure, we detected CD4-TCR complexes on the surface of the transformed human leukemia T cells, HPB-ALL, in the absence of stimulation. More than one CD4 were found in association with one TCR. CD4-TCR complexes were not in rapid equilibrium with free CD4 and free TCR, and they were not induced by the dye-labeled anti-CD4 or anti-TCR.

Production of autoantibodies by CD5-expressing B lymphocytes from patients with chronic lymphocytic leukemia

CD5-expressing B lymphocytes from patients with selected chronic lymphoproliferative disorders were used to determine whether monoclonal populations of CD5+ human B cells produce autoantibodies. CD5+ B cells from 19 patients with chronic lymphocytic leukemia (CLL) and one with diffuse well-differentiated lymphocytic lymphoma (DWDL) were cultured, with and without mitogenic stimulation, to obtain Ig from these cells. 17 of the 20 samples produced Ig in vitro. mAb from nine of the 17 patients were reactive with either IgG, ssDNA, or dsDNA. In every instance, the autoantibodies displayed monotypic L chain usage that correlated precisely with the L chain expressed on the CD5+ leukemic B cell surface. These monoclonal autoantibodies varied in their degree of antigenic specificity; some were quite specific, reacting with only one antigen, whereas others were polyspecific, reacting with two or all three autoantigens tested. Three features distinguish these autoantibodies from those observed in prior studies of CD5+ B cells. First, they are clearly the products of monoclonal populations of CD5+ cells; second, several react with dsDNA, a specificity not previously reported and often seen in association with significant autoimmune disorders; and third, two of the monoclonal autoantibodies secreted by the CD5+ clones were of the IgG class. Although not all of the Ig-producing, CD5-expressing clones elaborated mAbs reactive with the autoantigens tested, greater than 50% did. It is possible that with a broader autoantigenic panel or with larger quantities of CLL/DWDL-derived Ig, even more autoantibody-producing clones might be identified. These studies may have important implications for the antigenic specificity of subsets of human B lymphocytes as well as for lymphoproliferative and autoimmune disorders in general.

Intracellular accumulation of T-cell receptor complex molecules in a human T-cell line

This work was aimed at understanding the mechanisms of T-lymphocyte function by studying the cellular distribution and traffic of molecules of the T-cell receptor complex. The accumulation of specific molecules in intracytoplasmic vesicles is related to the activation of T lymphocytes. Some of these molecules include acid hydrolases, the transferrin receptor, and class I antigens of the major histocompatibility complex. Molecules of the T-cell receptor complex have now also been found in intracytoplasmic vesicles in a human T-cell line derived from a lymphoblastic leukemia. Such vesicles were tightly associated with the cytoplasmic microtubule network. One functional aspect of this association is a cellular pathway by which vesicles traveling to and from the cell surface converge in an area of the cells that is rich in processing enzymes.

Acidification of internalized class I major histocompatibility complex antigen by T lymphoblasts

It has previously been shown that activated murine T lymphocytes express intracellular vesicles containing the class I major histocompatibility complex (MHC) antigen H-2K. Evidence has also been provided that such vesicles may be part of a cellular pathway of spontaneous H-2K antigen internalization and recycling, which is specific to T-lymphoid cells. Dual fluorescence flow cytometry has now been used to establish that H-2K antigen is acidified upon internalization in concanavalin A-stimulated but not lipopolysaccharide-stimulated murine splenocytes, thus providing further support that in T lymphoblasts this class I MHC antigen may travel intracellular routes similar to those reported for other cell surface receptors.

Spontaneous internalization of Class I major histocompatibility complex molecules in T lymphoid cells

A low proportion of T lymphocytes in normal mouse spleen contains small intracytoplasmic vesicles showing Class I MHC molecules. After stimulation in vitro in a mixed lymphocyte reaction or by addition of Con A, the proportion of T cells with such intracytoplasmic vesicles increases progressively and becomes the majority. Labeling with fluorochrome-conjugated antibodies has shown that the vesicles are formed by internalization of molecules from the plasma membrane. The process is spontaneous and does not require cross-linking by antibodies or other ligands; it is selective inasmuch as other molecules (Thy-1 and T200 antigens) are not included and it is specific since it is not performed by other cells such as B lymphoid cells or fibroblasts. On the whole the process shows similarities with the internalization and recycling of other receptors, such as the receptors for different macromolecules of metabolic or informational significance, as seen in other cells. On the other hand, the specificity of Class I MHC mobilization in T lymphoid cells suggest a role for this process which is related to the immune function of these molecules.