Natural killer cell deficiencies in a consecutive series of children with herpetic encephalitis.

Natural killer (NK) cells play a fundamental role in innate and early phases of adaptive immunity against viral infections, both in humans and in animal models. To date, NK cell deficiencies in patients with severe herpetic infections have been reported in single cases, and their role as predisposing factor is still controversial. Five children affected by herpetic encephalitis were consecutively admitted to the Anna Meyer Children's Hospital in Florence (Italy) between 2003 and 2005. We therefore investigated the presence of NK cell deficiencies in a consecutive series of children with herpetic encephalitis. Five healthy children were included in the study as controls. Differential WBC counts, main Ig and IgE class serum analysis, cytofluorimetric analysis of circulating T, B and NK cells were performed on our study population. Sequencing of a selected region of CD16A gene transcript was carried out in two patients. All patients resulted to be affected by deficiencies related to NK cells in respect to controls. One patient was also affected by lymphopenia, while no other significant deficits of immunity were detected in the study population. To date, this is the first survey that demonstrates isolated NK cell deficiencies in a cohort of consecutive patients affected by severe herpes simplex infections. These findings suggest a role for NK cell deficiencies as a predisposing factor for increased susceptibility and severe course of disease in these patients.

Natural killer cell stimulatory factor (interleukin 12 [IL-12]) induces T helper type 1 (Th1)-specific immune responses and inhibits the development of IL-4-producing Th cells.

The effects exerted on the in vitro development of antigen-specific T cell lines and T cell clones by addition or neutralization of interleukin 12 (IL-12) in lymphocyte bulk culture were examined. T cell lines specific for Dermatophagoides pteronyssinus group I (Der p I) derived in the presence of IL-12 exhibited reduced ability to produce IL-4 and increased ability to produce interferon gamma (IFN-gamma), and developed into Der p I-specific CD4+ T cell clones showing a T helper type 0 (Th0)- or Th1-, instead of Th2-, like cytokine profile. In contrast, purified protein derivative (PPD)-specific T cell lines derived in the presence of anti-IL-12 antibody exhibited an increased ability to produce IL-4 and developed into PPD-specific CD4+ T cell clones showing a Th0-, instead of Th1-, like profile. The influence of IL-12 on the cytokine secretion profile of Der p I-specific T cell lines was not prevented by addition to lymphocyte bulk cultures of anti-IFN-gamma antibody, but could be at least partially inhibited by the removal from bulk cultures of CD16+ cells. Thus, IL-12 and CD16+ cells appear to have inhibitory effects on the development of IL-4-producing cells and to play an inductive role in promoting Th1-like responses.

Interleukin 12 induces stable priming for interferon gamma (IFN-gamma) production during differentiation of human T helper (Th) cells and transient IFN-gamma production in established Th2 cell clones.

Interleukin 12 (IL-12) facilitates the generation of a T helper type 1 (Th1) response, with high interferon gamma (IFN-gamma) production, while inhibiting the generation of IL-4-producing Th2 cells in polyclonal cultures of both human and murine T cells and in vivo in the mouse. In this study, we analyzed the effect of IL-12, present during cloning of human T cells, on the cytokine profile of the clones. The culture system used allows growth of clones from virtually every T cell, and thus excludes the possibility that selection of precommitted Th cell precursors plays a role in determining characteristics of the clones. IL-12 present during the cloning procedures endowed both CD4+ and CD8+ clones with the ability to produce IFN-gamma at levels severalfold higher than those observed in clones generated in the absence of IL-12. This priming was stable because the high levels of IFN-gamma production were maintained when the clones were cultured in the absence of IL-12 for 11 d. The CD4+ and some of the CD8+ clones produced variable amounts of IL-4. Unlike IFN-gamma, IL-4 production was not significantly different in clones generated in the presence or absence of IL-12. These data suggest that IL-12 primes the clone progenitors, inducing their differentiation to high IFN-gamma-producing clones. The suppression of IL-4-producing cells observed in polyclonally generated T cells in vivo and in vitro in the presence of IL-12 is not observed in this clonal model, suggesting that the suppression depends more on positive selection of non-IL-4-producing cells than on differentiation of individual clones. However, antigen-specific established Th2 clones that were unable to produce IFN-gamma with any other inducer did produce IFN-gamma at low but significant levels when stimulated with IL-12 in combination with specific antigen or insoluble anti-CD3 antibodies. This induction of IFN-gamma gene expression was transient, because culture of the established clones with IL-12 for up to 1 wk did not convert them into IFN-gamma producers when stimulated in the absence of IL-12. These results suggest that Th clones respond to IL-12 treatment either with a stable priming for IFN-gamma production or with only a transient low level expression of the IFN-gamma gene, depending on their stage of differentiation.

CD30 expression by CD8+ T cells producing type 2 helper cytokines. Evidence for large numbers of CD8+CD30+ T cell clones in human immunodeficiency virus infection.

A large panel of CD8+ T cell clones generated from peripheral blood lymphocytes (PBL) of healthy donors or human immunodeficiency virus (HIV)-infected individuals were assessed for both cytokine secretion profile and CD30 expression and release. The great majority of CD8+ T cell clones generated from healthy individuals showed the ability to produce interferon gamma (IFN-gamma), but not interleukin 4 (IL-4), and none of them either expressed membrane CD30 or released substantial amounts of soluble CD30 (sCD30) in their supernatant. In contrast, high numbers of CD8+ T cell clones generated from HIV-infected individuals, which produced IL-4 (and IL-5) in addition to IFN-gamma or IL-4 (and IL-5) alone, expressed membrane CD30 and released detectable amounts of sCD30 in their supernatants. Indeed, CD30 expression appeared to be positively correlated with the ability of CD8+ T cell clones to produce IL-4 and IL-5 and inversely correlated with their ability to produce IFN-gamma, whereas no correlation between CD30 expression and production of IL-10 was observed. These data suggest that CD30 is a marker for CD8+ T cells that have switched to the production of type 2 helper cytokines.

Th2-like CD8+ T cells showing B cell helper function and reduced cytolytic activity in human immunodeficiency virus type 1 infection.

We analyzed at clonal level the functional profile of circulating or skin-infiltrating T lymphocytes from two individuals infected with the human immunodeficiency virus type 1 (HIV-1), suffering from a Job's-like syndrome (eczematous dermatitis, recurrent skin and sinopulmonary infections, and hypergammaglobulinemia E) and showing virtually no circulating CD4+ T cells. Most of the CD3+ T cell clones generated from both patients were CD4- CD8+ TCR alpha beta +. The others were CD4- CD8- TCR alpha beta + which exhibited reduced mRNA expression for the CD8 molecule or no mRNA expression for either CD4 or CD8 molecules. The great majority of both CD4- CD8+ and CD4- CD8- did not produce interferon (IFN) gamma and exhibited reduced cytolytic activity. Rather, most of them produced large amounts of both interleukin (IL) 4 and IL-5 and provided B cell helper function for IgE synthesis. These data suggest that a switch of cytolytic CD8+ T cells showing a Th1-like cytokine secretion profile to cells that make Th2-type cytokines, exhibit reduced cytolytic potential, and provide B cell helper function can occur in the course of HIV-1 infection. These cells may contribute to the reduced defense against viral infections and intracellular parasites and account for the elevated IgE serum levels, eosinophilia, and the allergic-like clinical manifestations seen in a proportion of HIV-1-infected individuals.

Evaluation of a novel particle-based assay for detection of autoantibodies in idiopathic inflammatory myopathies.

BACKGROUND: Myositis specific antibodies (MSA) represent not only important diagnostic tools for idiopathic inflammatory myopathies (IIM), but also help to stratify patients into subsets with particular clinical features, treatment responses, and disease outcome. Consequently, standardization of MSA is of high importance. Although many laboratories rely on protein immunoprecipitation (IP) for the detection of MSA, IP standardization is challenging and therefore reliable alternatives are mandatory. Recently, we identified significant variation between IP and line immunoassay (LIA) for the detection of MSA and myositis associated antibodies. In this study we aimed to compare the results from our previous study to the results obtained with a novel fully automated particle-based technology for the detection of MSA and MAA. METHODS: A total of 54 sera from patients with idiopathic inflammatory myopathy (IIM) were tested using three methods: IP, LIA (Euroimmun, Germany) and a novel particle-based multi-analyte technology (PMAT, Inova Diagnostics, US, research use only). The analysis focused on antibodies to EJ, SRP, Jo-1, NXP-2, MDA5, TIF1-γ, and Mi-2. RESULTS: Significant variations were observed among all methods. Overall, the novel PMAT assays showed slightly better correlation with IP, but the kappa agreement was strongly dependent on the antibody tested. When the results obtained from IP were used as reference for receiver operating characteristic (ROC) curve analysis, good discrimination and a high area under the curve (AUC) value were found for PMAT (AUC = 0.83, 95% confidence interval, CI 0.70-0.95) which was significantly higher (p = .0332) than the LIA method (AUC = 0.70, 95% CI 0.56-0.84). CONCLUSION: The novel PMAT used to detect a spectrum of MSA in IIM represents a potential alternative to IP and other diagnostic assays. Additional studies based on larger cohorts are needed to fully assess the performance of the novel PMAT system for the detection of autoantibodies in myositis.

Influence of impaired T- and B-cell compartments on efficacy of IVIg in dysimmune neuropathies.

Autoimmune mechanisms are postulated to play a role in the development and progression of dysimmune neuropathies (DN). We investigated the relation between lymphocyte number and marker expression, and disease activity in 20 patients with DN under intravenous immunoglobulins (IVIg) treatment. B- and T-lymphocyte markers were studied by flow cytometry of the expression of CD5, CD25, CD23 and CD38 markers on B cells and of CD3, CD4 and CD8 markers, respectively. These parameters were compared with those obtained from matched healthy volunteers. The proportions of CD38+ B cells were higher in patients compared with those of controls. Proportions of activated CD4+ and CD8+ T cells were comparable in peripheral blood mononuclear cells of patients and controls, but a significant reduction of the absolute numbers of CD3+, CD4+ and CD8+ cells were observed in DN patients. The percentages of CD25+ memory T cells were instead significantly increased in DN patients. Lastly, T-cell reduction and the CD19/CD38 ratio over total B (CD19+) cells directly correlated with a poor response to IVIg therapy. In DN, whereas T-cell number is reduced, activated T and B cells are increased, thus suggesting an intrinsic defect of the immune response.

Role for CD30 in HIV expression.

CD30 is a member of the tumor necrosis factor (TNF)-receptor superfamily, whose ligand (CD30L) has been identified on B cells, activated macrophages and a subset of activated T cells. We show here that infection in vitro with human immunodeficiency virus (HIV) of CD4+ T-cell clones generated from HIV-seronegative individuals can enhance the expression of CD30, which often preceeds and is associated with the death of clonal T cells. Furthermore, cross-linking CD30 with an agonistic CD30-specific monoclonal antibody potentiated HIV replication induced by an insolubilized anti-CD3 antibody in T-cell lines generated from HIV-infected individuals. More importantly, paraformaldehyde-fixed CD8+ T-cell clones expressing CD30L enhanced HIV replication in anti-CD3-stimulated allogeneic or autologous HIV-infected CD4+ T-cell lines and such a potentiating effect was inhibited by an anti-CD30L antibody. The anti-CD30L antibody also exerted a suppressive effect on the spontaneous HIV replication occurring in lymph node cells, freshly derived from an HIV-seropositive patient showing CD30 expression in B cells and in a proportion of CD8+ T lymphocytes. Thus, CD30 triggering may play an important role in both HIV replication and the death of HIV-infected CD4+ T cells.

Different mitogenic activity of soluble and insoluble staphylococcal protein A (SPA).

The response to SPA and Staphylococcus strain Cowan I (StaCw) of highly purified populations of peripheral blood and tonsil human lymphocytes was investigated. Purified T lymphocytes isolated from perpheral blood by E-rosetting were unable to respond in vitro to StaCw. Highly purified B-cell populations from tonsils did not show any proliferative response in the presence of soluble SPA. The addition to highly purified B-cell suspensions from human tonsils of increasing concentrations of autologous T lymphocytes did not induce any increase of thymidine uptake in the presence of StaCw. However, it was able to restore a marked proliferative response of the B-cell cultures to soluble SPA, even though mitomycin-treated T lymphocytes were added. The low response of highly purified peripheral blood T lymphocytes to soluble SPA could be potentiated by the addition of autologous mitomycin-treated B cells, whereas the unresponsiveness of purified T lymphocytes to StaCw was not affected. Mitogenic activity of SPA coupled to Sepharose beads was different from that of soluble SPA and paralleled that of StaCw. These data strongly suggest that insoluble SPA is a T-cell-independent B-cell mitogen in man, whereas soluble SPA, like PWM, exerts its activity on B cells only in the presence of T cells.

Altered proportion of T mu-and T gamma-cell subpopulations in patients with Hodgkin's disease.

The ability of peripheral blood lymphocytes from patients with Hodgkin's disease (HD) to form rosettes with ox red blood cells (ORBC) sensitized by anti-ORBC purified rabbit IgM and IgG was investigated. The mean percentage of cells capable of forming rosettes with ORBC coated with IgM (EAIgM-RFC) in the peripheral blood of either untreated or X-ray-treated patients with HD was significantly lower than that of normal individuals. In the same groups of patients with HD the mean percentage of T lymphocytes equipped with receptor for IgG (T gamma lymphocytes), evaluated by a mixed fluorescent rosette assay, was significantly higher than in normal controls. These data suggest that the altered proportion between T mu-and T gamma-cell subpopulations in patients with HD probably represents a disease-related phenomenon.

Activation of human basophils by Staphylococcus aureus Cowan I. II. Alternative F(ab')-mediated mechanism.

We investigated the capacity of Staphylococcus aureus Cowan I (Cowan Staph A+) and Staphylococcus aureus Wood 46 (Wood Staph A-) to induce histamine release from human basophils in vitro. Cowan Staph A+ (3 X 10(6) to 3 X 10(8)/ml), which synthesizes protein A (Staph A), stimulated the release of histamine from basophils, whereas Wood Staph A- (3 X 10(6) to 3 X 10(9)/ml), which does not synthesize Staph A, did not induce histamine secretion. Soluble Staph A (10(-3) to 10 micrograms/ml) also induced histamine secretion from human basophils, Hyperiodination of Staph A, which destroys over 90% of the original Fc reactivity without altering the Fab binding site, did not alter this protein's ability to induce histamine release. The stimulating effect of Staph A was suppressed by preincubation with human polyclonal IgG and a human monoclonal IgM, which have F(ab')-Staph A reactivity. In contrast, rabbit IgG and a human monoclonal IgM possessing only Fc-Staph A reactivity did not inhibit Staph A activity. Preincubation with Staph A or Cowan Staph A+ resulted in complete cross-desensitization to a subsequent challenge with homologous and heterologous stimuli. These results indicate that Staph A and Cowan Staph A+ activate human basophils by interacting with the F(ab')2 region of IgE and/or IgG present on the cell surface.

Co-operation between T and B lymphocytes from human tonsils in the response to mitogens and antigens.

Purified B lymphocytes obtained from human tonsil cell populations by removing E rosette-forming cells by density sedimentation did not proliferate at three days in response to PHA and Con A, but showed a significant 3H-labelled thymidine incorporation when the PHA response was assessed at day 6 of culture. The 6th-day responses, which was completely abolished by the reduction of T-cell contamination to less than 0-1% by re-rosetting and a second separation, was due in part to a direct activation by PHA of contaminating T cells and in part to a T cell-mediated B-cell response. When purified B cells were stimulated for 3 days by PHA in the presence of an equal number of autologous or homologous mitomycin-treated T lymphocytes a highly significant uptake of 3H-labelled thymidine was demonstrated. The majority of blast cells obtained at day 4 in these cultures were unable to form E rosettes and showed surface immunoglobulin by immunofluorescence stain. This response was markedly decreased by previous treatment of B cells with mitomycin C and it was abolished when B cells were killed by heating at 56degrees C for 1 hr. Purified B lymphocytes from human tonsils did not respond in vitro when cultured for 6 days in the presence of soluble antigens (PPD and Candida). However, a highly significant response to the same antigens could be demonstrated when B cells were cultured in the presence of autologous mitomycin-treated T cells. These models of T-B co-operation could provide an interesting tool for studying the differentiation and antibody production in vitro of human B lymphocytes.

Mechanism of activation of human basophils by Staphylococcus aureus Cowan 1.

We investigated the capacity of Staphylococcus aureus Cowan 1 and S. aureus Wood 46 to induce histamine release from human basophils in vitro. S. aureus Cowan 1 (10(5) to 10(7)/ml), which synthesizes protein A (Staph A), stimulated the release of histamine from basophils, whereas S. aureus Wood 46 (10(5) to 2 X 10(7)/ml), which does not synthesize Staph A, did not induce histamine secretion. Soluble Staph A (10(-3) to 10 micrograms/ml), but not staphylococcal enterotoxin A, induced histamine secretion from human basophils. Staph A binds through its classical site to the Fc region of human immunoglobulin G (IgG) and through its alternative site to the Fab portion of the different human immunoglobulins. Hyperiodination of Staph A, which destroys over 90% of the original Fc reactivity without altering the Fab-binding site, did not alter the ability of the protein to induce histamine release. The stimulating effect of Staph A was dose dependently inhibited by preincubation with human polyclonal IgG (0.3 to 100 micrograms/ml) and a human monoclonal IgM (0.3 to 100 micrograms/ml) which have F(ab')-Staph A reactivity. In contrast, rabbit IgG, which possesses only Fc-Staph A reactivity, and a Staph A-unreactive human monoclonal IgM did not inhibit Staph A activity. Similar results were obtained with intact S. aureus Cowan 1. Preincubation with either Staph A or anti-IgE (rabbit anti-Fc epsilon) resulted in complete desensitization to a subsequent challenge with the homologous stimulus. Staph A and anti-IgE induced partial cross-densensitization to the heterologous stimulus. Cells preincubated with anti-IgG (rabbit anti-Fc gamma) lost a small but significant part of their ability to release with Staph A but did not lose their response to anti-IgE. Basophils from which IgE had been dissociated by brief exposure to lactic acid no longer released histamine in response to anti-IgE and Staph A. When basophils from which IgE had been dissociated were incubated with human polyclonal IgE, they regained their ability to induce histamine in response to Staph A and anti-IgE. In contrast, two monoclonal IgEs which do not bind to Staph A did not restore the basophil responsiveness to Staph A. Furthermore, there was complete cross-desensitization between soluble Staph A and S. aureus Cowan 1, while cells desensitized to S. aureus Wood 46 released normally with Staph A and S. aureus Cowan 1.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro production of IgE by human peripheral blood mononuclear cells. IV. Modulation by allergen of the spontaneous IgE antibody biosynthesis.

Peripheral blood lymphocytes (PBL) from a proportion of grass-sensitive patients, studied during or immediately after the grass pollination period, showed spontaneous production in vitro of grass-specific IgE antibody, whereas PBL from atopic patients sensitive to allergens other than grass pollens or non-atopic individuals did not. Pre-incubation of IgE antibody producing PBL from grass-sensitive patients with minute amounts of a mixed grass pollen (MGP) extract or Rye grass antigen Group I (Rye I) usually resulted in a reduction of the spontaneous production in vitro of IgE protein and in a marked inhibition of the spontaneous production in vitro of grass-specific IgE antibody. This antigen-specific inhibition was not mediated by T lymphocytes, but it was apparently due to a signal directly delivered by antigen to the spontaneously IgE antibody producing cells. The results support the concept that the activity of cells responsible for the persistent IgE antibody formation in vitro in atopic patients can be modulated by antigen.

Spontaneous in vitro differentiation of a myoepithelial cell line (PA 16/23) from a pleomorphic adenoma of the parotid gland is associated with reduced production of the autocrine growth factor interleukin 6.

A myoepithelial cell line (PA 16/23) was derived from a pleomorphic adenoma of the parotid gland. PA 16/23 cells have light microscopic, immunophenotypical and ultrastructural features of immature myoepithelial cells, i.e. they are of fusiform or stellate shape and show keratin and actin cytofilaments located mainly in the perinuclear cytoplasm, desmosomes and tracts of basal lamina. The PA 16/23 cells grew actively and expressed mRNA for and produced interleukin 6 (IL-6) which was released into the culture medium. This cytokine, in turn, acted as an autocrine growth factor on the cells. PA 16/23 cells also expressed high-affinity IL-6 receptors. In these cells, both IL-6 production and proliferation could be modulated by exogenous stimulants, such as IL-6 itself, IL-1, IL-4, tumour necrosis factor alpha, interferon gamma and lipopolysaccharide. From the 40th culture passage onwards, the PA 16/23 cells ceased to grow, either spontaneously or in response to exogenous stimulants. Moreover, they strongly reduced IL-6 production, and underwent morphological differentiation into more mature myoepithelial cells, with an increased amount and a different arrangement of the keratin and actin cytofilaments, which formed thick bundles in the peripheral cytoplasm. These findings suggest a role for IL-6 in modulating the proliferation and, possibly, the differentiation of the PA 16/23 cells.

Surface immunoglobulins are involved in the interaction of protein A with human B cells and in the triggering of B cell proliferation induced by protein A-containing Staphylococcus aureus.

The nature of surface components responsible for the reactivity of a subset of human B cells with staphylococcal protein A (SpA) was studied. The ability of normal non-T cells or non-T cells from patients with chronic lymphocytic leukemia (CLL) to form rosettes with human red blood cells coated with SpA (SpA-HRBC) was strongly inhibited or abolished by incubation with F(ab')2 fragments of antibodies against human immunoglobulin (Ig), whereas the incubation with F(ab')2 fragments of antibodies against a non-Ig cell surface antigen, such as beta 2-microglobulin, had no effect on the SpA-rosetting of human lymphocytes. The role of the reaction between surface Ig (sIg) and SpA in the triggering of the proliferative response induced by Staphylococcus aureus bacteria strain Cowan I (Cowan Staph) on normal or leukemic non-T cells was also investigated. A parallelism was observed between the mitogenic activity on normal human non-T cells of Cowan Staph and F(ab')2 fragments of immunosorbent-purified rabbit antibodies to human mu-chain. On the other hand, monovalent Fab fragments of anti-F(ab')2 or anti-mu chain antibodies were unable to activate human non-T lymphocytes, but usually induced a partial inhibition of the Cowan Staph-induced cell proliferation. Non-T cells from 2 patients with CLL did not respond to either Fab or F(ab')2 fragments of anti-Ig antibodies, but were stimulated to proliferate by Cowan Staph. However, the proliferative response of non-T cells from these patients to Cowan Staph was markedly inhibited or abolished by the addition to the cultures of F(ab')2 fragments of anti-Ig antibodies. Antibody preparations to human F(ab')2 or gamma-chain inhibited the response of IgG-bearing leukemic cells, whereas the Cowan Staph-induced proliferation of IgM-bearing leukemic lymphocytes was inhibited by the addition to the cultures of either anti-F(ab')2 or anti-mu chain antibodies. The proliferative response to Cowan Staph or normal non-T cells was also inhibited by the addition to the cultures of human and guinea pig polyclonal IgG, whereas IgG from other species, such as goat, ox, horse, and rabbit, were poorly or not at all inhibitory. On a molar basis, the F(ab')2 preparation from human IgG was as potent an inhibitor as intact IgG molecules, whereas Fc gamma was much less effective in inhibiting the Cowan Staph-induced cell proliferation. A monoclonal IgM, isolated from the serum of a patient with CLL, whose lymphocytes were able to form rosettes with SpA-HRBC and to proliferate in vitro after stimulation with Cowan Staph, also showed a marked inhibitory activity on the Cowan Staph-induced proliferation or normal non-T cells. These data suggest that an interaction between SpA present on the bacterial cell wall and a structure located in the Fab region of sIg, which is shared by sIgM, sIgG, and perhaps also by sIg of other classes, plays an important role in the triggering of B cell proliferation induced by SpA-containing staphylococci.

Human IL-10 is produced by both type 1 helper (Th1) and type 2 helper (Th2) T cell clones and inhibits their antigen-specific proliferation and cytokine production.

IL-10 gene transcription and IL-10 protein production was assessed in both type 1 (Th1) and type 2 (Th2) CD4+ human T cell clones by polymerase chain reaction and ELISA, respectively. Although Th2 clones apparently showed higher IL-10 mRNA levels, IL-10 mRNA expression was consistently found in Th1 clones, as well. Likewise, measurable IL-10 levels were found in the supernatants of both Th1 and Th2 clones. The effect of human IL-10 (h-IL-10) and viral IL-10 (v-IL-10) on the proliferative response and cytokine production by Th1 and Th2 human clones was also investigated. Addition in culture of h-IL-10 and v-IL-10 significantly reduced the proliferation of both Th1 and Th2 clones in response to the specific Ag and to PHA, but it had no inhibitory effect on the proliferative response of Th1 and Th2 clones to IL-2. h-IL-10 and v-IL-10 also inhibited the Ag-induced production of gamma-interferon (IFN-gamma) by Th1 clones and the production of IL-4 and IL-5 by Th2 clones, whereas they had no effect on the cytokine synthesis by the same clones stimulated with PMA plus anti-CD3 antibody. Preincubation of APC, but not of clonal T blasts, with h-IL-10 resulted in the inhibition of Ag-induced proliferation of both Th1 and Th2 clones, supporting the view that h-IL-10 primarily affects APC. These data demonstrate that, unlike the murine system where IL-10 is a product of Th2 (but not Th1) cells and seems to mainly down-regulate the Th1 response, in the human system, IL-10 is produced by, and down-regulates the function of, both Th1 and Th2 cells.

Alterations of both responder T cells and stimulator non-T cells are responsible for abnormal mixed lymphocyte reaction in aged humans.

The autologous and allogeneic mixed lymphocyte reactions of 15 young and 15 aged human adults were compared. Both autologous and allogeneic mixed lymphocyte reactions were significantly reduced in the aged group. T cells from aged adults displayed a reduced proliferative response to non-T cells of either aged or young adults. T cells from young adults also showed a reduced proliferative response to non-T cells from aged adults. Sera from aged adults, showing depression of autologous and allogeneic mixed lymphocyte reaction, did not exert any inhibitory effect on the autologous and allogeneic mixed reaction of lymphocytes from young donors. These data suggest that depression of mixed lymphocyte reaction in aged humans probably reflects intrinsic abnormalities of both responder T cells and stimulatory non-T cells.