Relationship of Fc-IgG and Fc-IgM receptors to the antigens defined by OKT-Antibodies and the acid α-naphthyl-acetate-esterase spot within human T cells

The expression of receptors for Fc-IgG and Fc-IgM on human T cells was correlated to the antigens recognized by monoclonal antibodies of the OKT series (T3, T4, T8, I1, M1) and to the presence of the dot-like cytoplasmic α-naphthyl-acetate-esterase activity (ANAE). ANAE spots were demonstrated in cyto-centrifuged smears; Fc-receptors (Fc-R) were shown using rosetting techniques which also served to enrich the respective cell populations; OKT antigens were detected by indirect immunofluorescence and OKT4 or OKT8-enriched subsets were obtained by antibody and complement-dependent lysis. Total T and Fc-IgM-R expressing T cells had a similar distribution of OKT antigens (90-95% T3⁺, ～ 60% T4⁺, ～ 30% T8⁺, ? 9 % M1⁺). The Fc-IgG-R expressing T-cell fraction differed in that it contained less OKT3⁺ cells (72 %), about 34 % OKM1⁺ cells and had an elevated percentage of OKT8⁺ cells (53 %). Similarly, OKT8-enriched cell fractions expressed more Fc-IgG-R (44 %) than unseparated T cells (12 %) or OKT4-enriched T-cell populations (16 %). Modulation of the Fc-IgG-R by exposure to immune complexes did not alter the expression of OKT antigens. Fc-IgG-R were, however, not restricted to OKT8⁺ cells, as simultaneous visualization of OKT antigens and Fc-R revealed that 7-11 % of OKT4⁺ cells were also Fc-IgG-R-positive. Thus Fc-IgG-R appear to be preferentially expressed on OKT8⁺ cells, but also OKT4⁺ cells were able to express Fc-IgG-R.As regards the dot-like ANAE activity, T cells expressing Fc-IgM-R exhibited 80-90 % of ANAE positivity, whereas only 20-30% of the Fc-IgG-R-bearing T cells were ANAE⁺. Stimulation of T cells expressing Fc-IgM-R with ConA led to a dramatic drop in the percentage of ANAE⁺ cells after 48 to 72 hrs (80 % to 20 %) suggesting that this cytochemical marker is lost during blast transfonnation. Enrichment for OKT4⁺ and OKT8⁺ subsets, on the other hand, did not result in significantly altered percentage of ANAE + cells compared to the unseparated T cells as (OKT4⁺ were to 88 % and OKT8⁺ to 73 %) ANAE-positive.These data demonstrate that OKT antigens as well as Fc-IgG-R, Fc-IgM-R, and the ANAE spot are T-cell markers defining different aspects of T-cell function. This does not rule out that certain markers correlate to each other: their combined application may be useful further to dissect the T cell system.     

Evidence for the ontogenic precedence of suppressor T cell functions in the human neonate

The study was undertaken to elucidate some functional characteristics of T cell subsets in human cord blood. A comparison of the cellular interactions involved in the in vitro regulation of pokeweed (PWM) vs. Epstein-Barr virus (EBV)-driven B cell differentiation was done in vitro in short-term cultures of lymphocytes from newborns or adults. T cell subsets were isolated using the monoclonal antibodies OKT4⁺ and OKT8⁺. OKT4⁺ but not OKT8⁺ T lymphocytes from adults as well as neonates suppressed EBV-induced immunoglobulin (Ig) secretion of B lymphocytes from adults. This inhibition was mediated through gamma-type interferon (IFN-γ). B cells from newborns were not inhibitable by OKT4⁺ lymphocytes as a result of their insensitivity to IFN-γ. Helper activity for PWM-induced Ig secretion was exclusively contained within the OKT4⁺ population from adult T cell donors. This function was normally not detectable in any of the neonatal T cell subsets. OKT8⁺ cells from both adults and neonates suppressed PWM-induced Ig secretion, but required the collaboration with cells within the OKT4⁺ population. The suppressor activity in the PWM system was not IFN-γ-mediated. Thus, suppressor functions for EBV-vs. PWM-induced Ig synthesis were mediated through different pathways. There was no evidence of a unique suppressor system in the newborn. In the neonate, suppressor T cell activities are developed before T helper functions, a circumstance for which there is good evolutionary reason.     

Human Fetal/Neonatal Suppressor Activity: Relation Between OKT Phenotypes and Sensitivity to Prostaglandin E2 in Maternal and Neonatal Lymphocytes

ABSTRACT: T lymphocytes from human fetuses and newborns strongly and spontaneously suppress various adult cell functions (i.e. T-cell proliferation, B-cell differentiation, and Ig synthesis). The precise phenotype of the suppressor cell is controversial. In this investigation we use cord T-cell subsets negatively selected by the panning technique or by complement-mediated lysis using the monoclonal antibodies OKT4 and OKT8. Cord T cells deprived of the OKT4⁺ subpopulation exerted only a marginal suppressor activity (12 ± 7 as compared to 73 ± 4% of unfractionated T cells) on the proliferation of maternal cells in our PHA-stimulated co-culture assay using sex chromosomes as markers for dividing cord (male) and maternal cells. The suppressive effect was direct, i.e. not mediated by induction of maternal OKT8⁺ suppressor effector cells. Cord and maternal T-cell subsets were also tested for their sensitivity to exogenous prostaglandin E₂ (PGE₂) at doses varying between 1.4 × 10^?5 and 1.4 × 10^?9 M. Both maternal OKT4^? and OKT8^? T-cell subsets were highly sensitive to suppression by PGE₂. In contrast, cord OKT8^? T cells were essentially nonsensitive at all doses of PGE₂ used, whereas cord OKT4^? T cells were significantly suppressed at four out of five concentrations tested (1.4 × 10^?6 through 1.4 × 10^?9). Our results suggest a direct correlation between the phenotypes of the cord-suppressor and maternal-target T cells and their sensitivity to PGE₂.     

The In Vitro Effect of a Calf Thymus Extract (Thymostimulin) on T Cell Phenotypes in Cord Blood Lymphocytes

ABSTRACT: An investigation was carried out on the in vitro effect of a calf thymus extract, thymostimulin, on the distribution of T cell phenotypes as defined by OKT3, OKT4, and OKT8 murine monoclonal antibodies and on E-rosetting cells in human cord blood lymphocytes from healthy newborns. The percentages of E-rosette-forming lymphocytes and OKT3⁺ total T population were lower in newborns than in adults (E-rosettes: 43.8% ± 13% vs 57.9% ± 7.9%, p < 0.01; OKT3⁺ cells: 53.3% ± 15.5% vs 79.9% ± 4.7%, p < 0.01), while the OKT4⁺/OKT8⁺ (helper/suppressor) cell ratio was normal in both (newborns: 3.40; adults: 2.44—NS). Thymostimulin increased the number of E-rosette-forming cells from 43.8% ± 13% to 49.9% ± 12.7% (p < 0.01), as well as the percentage of phenotypic T lymphocytes. The highest increases were observed in the OKT4⁺ cells (37.7% ± 14% to 49.1% ± 13.8%, p < 0.001), while smaller changes were observed in the OKT3⁺ cells (53.3% ± 15.5% to 58.1% ± 13.3%, p < 0.02) and OKT8⁺ cells (12.8% ± 6.4% to 16.6% ± 6.5%, p < 0.02). The results of the present study suggest that thymostimulin mainly provokes an increase in the helper T cell phenotype in cord blood lymphocytes.     

T cell subset alterations in idiopathic glomerulonephritis

Peripheral blood lymphocytes from 15 healthy controls and 59 patients with idiopathic glomerulonephritis were studied to determine whether an imbalance exists among human T cell subsets in these diseases. Twenty of the patients studied had a minimal change nephropathy (10 with nephrotic syndrome and 10 in sustained remission); 27 had a membranous glomerulonephritis (12 with nephrotic syndrome, six with isolated proteinuria and nine in complete remission); 12 patients had an IgA glomerulonephritis with heamaturia and mild proteinuria. Monoclonal antibodies directed at human T lymphocyte subsets termed OKT3, OKT4 and OKT8 were used in an indirect immunofluorescence assay in all cases. Patients with minimal change nephropathy, with or without nephrotic syndrome and patients with IgA glomerulonephritis showed mean values of OKT3⁺ cells (total peripheral T cells), helper OKT4⁺ cells, suppressor OKT8⁺ cells and OKT4⁺/OKT8⁺ cell ratio, in the normal range. Only the group of patients with membranous glomerulonephritis and nephrotic syndrome presented a mean OKT4⁺/OKT8⁺ ratio greater than the normal group (percentages: 2·43±0·3 vs 1·6±0·1 s.e.m.; P<0·02). This increased ratio was due to a reduction in the OKT8⁺ cell subset compared to the healthy subjects (percentages: 27·6±2·9 vs 36·8±1·4 s.e.m.; P<0·01). Our data shows that the functional lymphocyte disorders previously described in minimal change nephropathy and IgA glomerulonephritis are not due to a numerical imbalance of lymphocyte subsets. Such an imbalance of lymphocyte subsets was specifically observed in membranous glomerulonephritis with nephrotic syndrome. The true significance of this finding has to be clarified by longitudinal studies and functional tests.     

A mature thymocyte-like phenotypic pattern on human cord circulating T-lymphoid cells

Cord blood samples from healthy full-term newborns were tested with antimature and antiimmature lymphoid-cell monoclonal antibodies, as well as more traditional markers, in order to identify the phenotype of circulating precursor cells. The results demonstrated that human cord blood contains a lower number of OKT3⁺, E-rosetting mature T cells than adult blood, very high levels of OKT10⁺ cells, and few OKT9⁺, OKT8⁺OKT3^–, and OKT4⁺OKT3^– cells. Although the finding of OKT9⁺ and OKT10⁺ cord circulating cells could be indicative of cell activation, double marker studies in newborn blood pointed to phenotypically immature lymphoid subsets at different stages of maturation, according to Reinherz's hypothesis. In addition, the absence of nuclear Tdt-positive and hot-rosetting cells, together with the fact that most of these are OKT3⁺, OKT10⁺, OKT4⁺, or OKT8⁺ cells, suggests that the surface phenotype of newborn lymphocytes is similar to that of mature thymocytes.     

IFNβ-1a therapy for multiple sclerosis expands regulatory CD8 T cells and decreases memory CD8 subset: A longitudinal 1-year study

The beneficial effects of interferon β-1a (IFNβ-1a) in multiple sclerosis (MS) remain only partially understood. CD8⁺ T cells are key cells in MS pathogenesis that contribute to axonal damage in MS, whereas CD4⁺ regulatory T cells (T_Reg) and CD8⁺ regulatory/suppressor T cells (Ts) play an important role in protecting against subsequent MS activity. We analysed ex vivo changes on T_Reg and on the different subsets of CD4⁺ and CD8⁺ T lymphocytes, before IFNβ-1a (Rebif) therapy and at 3, 6, and 12 months after treatment, in 23 MS patients and in 26 healthy controls. IFNβ-1a significantly increased the proportions of CD4⁺ T_Reg and regulatory CD8⁺ T cells (Tr). Memory CD8⁺ T cells were significantly decreased after 1 year of treatment, maybe reflecting down-regulation of abnormally persistent systemic activation in MS patients. After 1 year of IFNβ-1a, a direct correlation was observed between plasmacytoid dendritic cells and effector CD8⁺ T cells.     

Monoclonal antibodies against HLA-DR antigens acting on stimulator cells prevent OKT8+ T lymphocytes from acquiring sensitivity to interleukin 2 and expressing suppressor function

Purified OKT8⁺ but not OKT4⁺ T lymphocytes generated suppressor activity in autologous mixed lymphocyte reactions (AMLR) in the presence but not in the absence of interleukin 2 (IL 2) as determined in proliferative responses of peripheral blood mononuclear cells induced by Concanavalin A, the OKT3 monoclonal antibody and allogeneic cells (indicator systems for suppressor activity used in this study). Furthermore, treatment of AMLR-activated T cells with the OKT8 antibody plus complement abolished suppressor cell activity whereas treatment of the cells with the OKT4 antibody plus complement did not. The three monoclonal anti-HLA-DR antibodies used in this study abrogated the induction, but not the effector phase, of suppressor cells in AMLR. The anti-DR antibodies acted specifically on the stimulator non-T cells and not on the responder T cells. The addition of IL2 to AMLR cultures performed in the presence of the anti-DR antibodies did not restore or increase the suppressor activity whereas IL2 added to AMLR cultures exposed to control antibodies or medium alone increased the suppressor activity. Moreover, purified OKT8⁺ T cells cocultured with autologous non-T cells and IL2, in the presence of the anti-DR antibodies, neither responded to IL2 by proliferating nor expressed suppressor function. In contrast, OKT8⁺ T cells from similar cultures, but performed in the absence of the anti-DR antibodies or exposed to control antibodies, proliferated to IL2 stimulation and exhibited suppressor activity. Unactivated OKT8⁺ T cells were unresponsive to IL2 and unable to express suppressor function. Finally, the addition of the OKT8 antibody (in the absence of complement) to AMLR cultures had no effect on the generation of suppressor cells. From these results, we conclude the following: (a) OKT8⁺ T lymphocytes become sensitive to IL2 by interacting with HLA-DR antigens on the stimulator non-T cells and, with the help of IL2, they express suppressor cell activity; (b) the OKT8 antigenic determinant on AMLR-activated suppressor cells does not seem to participate in their process of activation; (c) results of previous studies showing that OKT4⁺ T lymphocytes become sensitive to IL1 and are capable of synthesizing IL2 after interaction with HLA-DR on the stimulator cells, and the findings presented here, lead us to suggest that both OKT4⁺ and OKT8⁺ T lymphocytes possess receptors for self HLA-DR antigens and that neither the OKT8 nor the OKT4 antigenic determinants on these cells are involved in the recognition of HLA-DR antigens. The suppressor activity generated in AMLR may be one mechanism whereby effector self-tolerance is maintained in the face of inductive self-recognition.     

Epstein–Barr virus effect on frequency of functionally distinct T cell subsets in children with infectious mononucleosis

PurposeEpstein–Barr virus is a common human pathogen which infects the great majority of population worldwide. A striking proliferation of CD8⁺ T cells is an immune response to EBV invasion of B lymphocytes during infectious mononucleosis. The aim of the study was to analyze frequencies of CD28⁺CD95⁻, CD28⁺CD95⁺, CD28⁻CD95⁺ T cell subsets putative naïve (T_N), central (T_CM) and effector memory (T_EM) T cells in children with infectious mononucleosis.Material/methodsMultiparameter flow cytometric analysis of CD4⁺ and CD8⁺ T cell subsets was performed in 19 children with acute infectious mononucleosis.ResultsThe CD4⁺/CD8⁺ ratio was found to be decreased (0.53) in children with infectious mononucleosis. Median T_N, T_CM, T_EM frequencies were estimated to be 3.7, 4.5, 15.1% of CD8⁺ and 23, 59.3, 5.5% of CD4⁺ T cells, respectively. In the present study we demonstrated negative correlations between CD8⁺CD28⁺CD95⁺ and CD8⁺CD28⁻CD95⁺ T cells and both VCA IgM antibody titers and disease duration. However, no such correlation was found when subset of CD4⁺ T cells or CD8⁺CD28⁺CD95⁻ cells was compared.ConclusionsWe conclude that there is a rapid decrease in the number of memory CD8⁺ T cells in early acute stage of infectious mononucleosis.     

CD4+ CD25+ Treg regulate the contribution of CD8+ T-cell subsets in repopulation of the lymphopenic environment

Peripheral T‐cell expansion is of major relevance for immune function after lymphopenia. In order to promote regeneration, the process should result in a peripheral T‐cell pool with a similar subpopulation structure as before lymphopenia. We investigated the repopulation of the CD8⁺ central‐memory T cells (T_CM) and effector‐memory T cells (T_EM) pools after adoptive transfer of sorted CD8⁺ T cells from naïve, T_CM and T_EM subsets into T‐cell‐deficient hosts. We show that the initial kinetics of expansion are distinct for each subset and that the contribution to the repopulation of the CD8⁺ T‐cell pool by the progeny of each subset is not a mere function of its initial expansion. We demonstrate that CD4⁺CD25⁺ Treg play a major role in the repopulation of the CD8⁺ T‐cell pool and that CD8⁺ T‐cell subsets impact on each other. In the absence of CD4⁺CD25⁺ Treg, a small fraction of naïve CD8⁺ T cells strongly proliferates, correlating with further expansion and differentiation of co‐expanding CD8⁺ T cells. CD4⁺CD25⁺ Treg suppress these responses and lead to controlled repopulation, contributing decisively to the maintenance of recovered T_CM and T_EM fractions, and leading to repopulation of each pool with progeny of its own kind.     

Identification of lymphocyte subsets in peripheral blood and thyroid gland in Graves' disease by alpha-naphthyl-acetate-esterase reaction

T lymphocyte subsets were prospectively examined in the peripheral blood and thyroid aspirates of 10 patients with hyperthyroid Graves' disease before and after treatment with methimazole and attainment of euthyroidism. T lymphocyte subsets were identified with monoclonal antibodies and pattern of alpha-naphthyl-acetate esterase (ANAE) staining pattern in the case of peripheral blood and ANAE staining pattern with thyroid aspirate smears. Before treatment, OKT8+ lymphocytes were significantly decreased (18.4% +/- 4.8) (S. D.) in the patients compared to control (28.8 +/- 6.7%, p less than 0.05), the OKT4/OKT8 ratio was increased (2.92 vs 2.11). Percent OKT8+ lymphocytes were not different from the controls when the ten patients had been rendered euthyroid. ANAE mononuclear cells with a diffuse pattern (presumed suppressor cells) were 4.2% +/- 1.8 before treatment and 8.3 +/- 2.4 (p less than 0.05) after treatment and 11.5% +/- 2.2 in controls. ANAE mononuclear cells with diffuse pattern represented 4.2% +/- 1.8 of the mononuclear cells infiltrating the thyroid gland of untreated patients and rose to 8.3% +/- 2.4 after the patients had become euthyroid. ANAE negative cells (B cells and some T cells) were increased in the thyroid of untreated patients. It is concluded that mononuclear cells with presumed suppressor T cell phenotype are decreased in the blood and thyroid glands of patients with active Graves' disease and that this defect is corrected when euthyroidism has been established.     

Characterization of human interferon-gamma-producing leukocytes with monoclonal antileukocyte antibodies

Monoclonal antibodies with specificities for subsets of human leukocytes have been used for the characterization of interferon (IFN)γ-producing cells. The production of IFNγ was demonstrated to be a function of OKT3⁺ T lymphocytes. The capacity to secrete IFNγ was not restricted to the OKT4⁺ or the OKT8⁺ T-cell subset. BA-1⁺ B lymphocytes and Leu7⁺ natural killer cells did not contribute to the production of IFNγ. Ia⁺, OKM1⁺ monocytes served an auxiliary function in the production of IFNγ. The requirement for accessory monocytes, however, was not absolute, because monocyte-free preparations of long-term cultured IL2-dependent T lymphocytes retained the capacity to secrete IFNγ.     

Immunosuppressive evidence of Tityus serrulatus toxins Ts6 and Ts15: insights of a novel K+ channel pattern in T cells

The voltage‐gated potassium channel Kv1.3 is a novel target for immunomodulation of autoreactive effector memory T cells, which play a major role in the pathogenesis of autoimmune diseases. In this study, the Ts6 and Ts15 toxins isolated from Tityus serrulatus (Ts) were investigated for their immunosuppressant roles on CD4⁺ cell subsets: naive, effector (T_EF), central memory (T_CM) and effector memory (T_EM). The electrophysiological assays confirmed that both toxins were able to block Kv1.3 channels. Interestingly, an extended Kv channel screening shows that Ts15 blocks Kv2.1 channels. Ts6 and Ts15 significantly inhibit the proliferation of T_EM cells and interferon‐γ production; however, Ts15 also inhibits other CD4⁺ cell subsets (naive, T_EF and T_CM). Based on the Ts15 inhibitory effect of proliferation of all CD4⁺ cell subsets, and based on its blocking effect on Kv2.1, we investigated the Kv2.1 expression in T cells. The assays showed that CD4⁺ and CD8⁺ cells express the Kv2.1 channels mainly extracellularly with T_CM cells expressing the highest number of Kv2.1 channels. We also provide in vivo experimental evidence to the protective effect of Ts6 and Ts15 on delayed‐type hypersensitivity reaction. Altogether, this study presents the immunosuppressive behaviour of Ts6 and Ts15 toxins, indicating that these toxins could be promising candidates for autoimmune disease therapy. Moreover, this is the first report illustrating the involvement of a novel K⁺ channel subtype, Kv2.1, and its distribution in T‐cell subsets.     

Thein vivo effects of corticosteroids on thymocyte subsets in myasthenia gravis

Thein vivo effects of corticotherapy on thymocyte subpopulations have been evaluated in patients with myasthenia gravis (MG). Ten patients receiving high-dose, long-term treatment were studied and compared with two control groups (MG untreated patients and normal agematched subjects). In the treated group, the thymus was generally involuted; the percentage of OKT6⁺ or OKT4⁺T8⁺ thymocytes was profoundly decreased compared to controls. A significant percentage of OKT10^– cells was detected particularly among older patients, suggesting steroid-induced immigration. Conversely the percentage of more mature OKT3⁺ cells was increased. The balance between OKT4⁺T8^– and OKT4^–T8⁺ cells was unchanged in young patients (<40 years old) and increased in the older group. These data show that, as in the mouse, corticosteroids profoundly alter human thymocyte subsets.     

Ultrastructural characteristics of human T cell clones with various cytolytic activities

Fifteen T cell clones with different (specific, antibody-dependent or natural killer-like) cytolytic activity were derived from mixed lymphocyte culture activated T cells and analyzed for their morphological characteristics and, in some instances, for their surface markers. All of the five cytolytic clones analyzed by electron microscopy possessed numerous electron-dense granules and in some instances multivesicular bodies, with or without an electron-dense matrix, that are the putative precursors of the granules. In addition, light microscopy examination of semithin sections of other ten cytolytic clones showed that the large majority of the cells in each clone had numerous toluidine blue-stained cytoplasmic granules. It is of note that nine clones without detectable cytolytic activity analyzed by electron microscopy did not possess granules and presented the features of large agranular blasts. Ten cytolytic clones were analyzed for different surface markers including rosette formation with sheep erythrocytes (E rosettes), receptors for the Fc portion of IgG or IgM (FcγR and FcμR) and a group of antigens recognized by monoclonal antibodies including Ia, 4F2, OKT8 or OKT4. All the clones were Erosette⁺, Ia⁺ and 4F2⁺. Expression of FcγR was restricted to the clones active in antibody-dependent cell-mediated cytotoxicity. Expression of OKT8 and OKT4 antigens was variable; in particular, five clones were OKT8⁺/OKT4^?, whereas the other five expressed the OKT8^?/OKT4⁺ phenotype. It is noteworthy that the ultrastructural features of cytolytic T cell clones are similar to those of large granular lymphocytes, known to be the only lymphoid cells in normal peripheral blood which possess cytolytic activity. Thus, it is possible that the presence of electron-dense granules may represent a morphological marker for all human cytolytic lymphocytes.     

Generation of specific effector and memory T cells with gut- and secondary lymphoid tissue- homing potential by oral attenuated CVD 909 typhoid vaccine in humans

Induction of effective memory T cells is likely to be critical to the level and duration of protection elicited by novel live oral typhoid vaccines. Using cells from volunteers who ingested Salmonella Typhi vaccine strain CVD 909, we characterized the induction of interferon (IFN)-γ-secreting central (T_CM, CD45RO⁺CD62L⁺) and effector (T_EM, CD45RO⁺CD62L⁻) memory T populations, and their gut-homing potential based on integrin α4/β7 expression. Both CD4⁺ T_EM and T_CM populations secreted IFN-γ. However, although CD4⁺ T_EM expressed, or not, integrin α₄/β₇, CD4⁺ T_CM cells were predominantly integrin α₄/β₇⁺. In contrast, IFN-γ-secreting CD8⁺ cells were predominantly classical T_EM and CD45RA⁺ T_EM (T_EMRA, CD45RO⁻CD62L⁻) subsets. However, although CD8⁺ T_EM expressed, or not, integrin α₄/β₇, CD8⁺ T_EMRA were predominantly integrin α₄/β₇⁺. This is the first demonstration that oral immunization of humans with S. Typhi elicits diverse IFN-γ-secreting CD4⁺ and CD8⁺ T_CM and T_EM subsets able to migrate to the gut and other lymphoid tissues.     

Association between discordant immunological response to highly active anti‐retroviral therapy,regulatory T cell percentage,immune cell activation and very low‐level viraemia in HIV‐infected patients

The mechanisms sustaining the absence of complete immune recovery in HIV‐infected patients upon long‐term effective highly active anti‐retroviral therapy (HAART) remain elusive. Immune activation, regulatory T cells (T_regs) or very low‐level viraemia (VLLV) have been alternatively suspected, but rarely investigated simultaneously. We performed a cross‐sectional study in HIV‐infected aviraemic subjects (mean duration of HAART: 12 years) to concomitantly assess parameters associated independently with inadequate immunological response. Patients were classified as complete immunological responders (cIR, n = 48) and inadequate immunological responders (iIR, n = 39), depending on the CD4⁺ T cell count (> or < 500/mm³). Clinical and virological data (including very low‐level viraemia) were collected. In parallel, immunophenotyping of CD4⁺ lymphocytes, including T_reg subsets, and CD8⁺ T cells was performed. Percentages of activated CD4⁺ T cells, T_regs, effector T_regs and terminal effector T_regs were found to be significantly elevated in iIR. Neither the percentage of activated CD8⁺ T cells nor VLLV were found to be associated with iIR. In the multivariate analysis, nadir of CD4⁺ T cell count and percentage of T_regs were the only two parameters associated independently with iIR [odds ratio (OR) = 2·339, P = 0·001, and OR = 0·803, P = 0·041]. We present here the largest study investigating simultaneously the immune response to long‐term HAART, activation of CD4⁺ and CD8⁺ T cells, T_reg percentages and very low‐level viraemia. Causative interactions between T_regs and CD4⁺ T cells should now be explored prospectively in a large patients cohort.     

Regulatory T cell-subset imbalance in chronic active hepatitis

Three monoclonal anti-T-cell antibodies, specifically directed against total T cells (OKT3), inducer-helper T cells (OKT4), and suppressor/cytotoxic T cells (OKT8), were used in this study to analyze peripheral T-cell subsets in hepatitis B surface antigen (HBsAg)-positive and -negative chronic active hepatitis (CAH) patients. Results showed that a clear-cut difference exists in the distribution of peripheral T cells of these two groups of subjects. HBsAg-positive CAH patients had a numerical predominance of peripheral T lymphocytes expressing the characteristics of cytotoxic/suppressor T cells. In contrast, patients with autoimmune HBsAg-negative CAH exhibit a predominance of OKT4⁺ T cells, namely, the helper-inducer T-cell subset. In addition, high numbers of circulating doubly labeled cells (expressing both the OKT4 and the OKT8 xenoantigens) were detected in some of the HBsAg-positive and HBsAg-negative CAH patients studied.     

Lymphocyte subsets in human adenoids and tonsils. Rosette formation, alpha-naphthyl acetate esterase cytochemistry, monoclonal antibodies and peanut lectin reactivity

The distribution of mononuclear cell subsets has been studied in human adenoids, tonsils and peripheral blood (PB) by evaluating the presence of surface immunoglobulins, E-rosette formation, receptors for IgG Fc and for complement, alpha-naphthyl acetate esterase (ANAE) cytochemistry, reactivity with peanut lectin (PNA) and with monoclonal antibodies (McAb) (OK panel). Adenoids and tonsils, compared to PB, contain (1) fewer macrophages and T cells but more B cells; (2) higher proportions of ANAE negative, complement receptors and Ia-like antigens bearing T lymphocytes; (3) higher percentages of cells reacting with the McAbs OKT9 and OKT10 ("immature" lymphoid cells). In both adenoids and tonsils, clusters, formed by a central heavily ANAE stained interdigitating cell surrounded by lymphocytes with a sickle-shaped ANAE reaction, were found. Analogous clusters have been previously described in mice and human thymus. Two major hypotheses could be put forward: (1) adenoids and tonsils contain "immature" lymphoid cells undergoing education process, or (2) the above organs contain lymphocytes activated by a constant exposure to bacterial antigens or mitogens.     

In vitro evaluation of γδ T cells regulatory function in Behçet’s disease patients and healthy controls

CD8-positive γδ T lymphocytes (GDCD8⁺) are specifically increased in peripheral blood of Behçet’s disease (BD) patients. GDCD8⁺ have shown a T regulatory (T_reg) function in autoimmune experimental models, human tumor infiltrates and intestinal intraepithelial lymphocytes from celiac patients. The aim of this study was to evaluate the T_reg function of GDCD8⁺ and GDCD8⁻, freshly isolated from peripheral blood, in comparison to CD4⁺CD25^high naturally occurring T_reg cells (nT_reg) in BD and healthy controls (HC).We tested their suppressive activity on CD4⁺CD25⁻ T effector cells (T_eff) proliferation by a CFSE dilution protocol, after suboptimal activation with anti-CD3, in the absence or presence of IL-2. Furthermore, secreted cytokines and suppressive latency associated peptide (LAP)-TGFβ surface upregulation were determined after GD activation.We found that Vδ1 chains contribution to GDCD8⁺ was higher in BD than in HC, but neither GDCD8⁺ nor GDCD8⁻; (i) suppressed T_eff proliferation, (ii) expressed LAP-TGFβ (iii) nor secreted IL-10, in either group. Moreover, GD presented a proinflammatory cytokine profile, mainly producing IFNγ and TNFα, in contrast to nT_regs.In conclusion, peripheral GD could contribute more to the dysregulation of TH1 type of cytokines than to exerting a T_reg function in BD.