CD45RB expression defines two interconvertible subsets of human CD4+ T cells with memory function

Reciprocal expression of CD45RA and CD45RO in human CD4⁺ T cells defines populations understood to be naive cells (CD45RA⁺CD45RO^?) and memory cells (CD45RA^?CD45RO⁺). We investigate two subsets of CD45RA^?CD45RO⁺ CD4⁺ human T cells which differ by fourfold in their expression of the CD45RB isoform; one is CD45RB^bright and the other is CD45RB^intermediate. In contrast, CD45RA⁺ naive cells are all CD45RB^bright. Both subsets of CD45RA^? cells proliferate in response to recall antigens so we designate them MEM 1 (CD45RO⁺RB^bright) and MEM 2 (CD45RO⁺RB^intermediate). CD45RA and CD45RB expression are regulated independently during in vitro activation of naive cells. When MEM 1 cells are activated they tend to down-regulate CD45RB expression, whereas activated MEM 2 cells tend to up-regulate CD45RB expression. Thus, in contrast to the stability of the CD45RA^?CD45RO⁺ phenotype, the MEM 1 and MEM 2 phenotypes are labile and may interconvert. MEM 1 and MEM 2 cells produced comparable amounts of interleukin(IL)?2, IL?4, and IL-5 though MEM 1 cells produced slightly more interferon(IFN)-γ (mean 1.7-fold more). MEM 1 cells consistently proliferated more (mean 2.3-fold more) than MEM 2 cells early during in vitro activation. Thus, differential expression of CD45RB within CD45RA^? cells defines two subsets that have similar properties except for somewhast greater IFN-γ production and proliferative responses by MEM 1 cells. Variability in CD45RB expression may represent a mechanism for fine-tuning the responsiveness of memory cells in vivo.     

CD57+ T lymphocytes are derived from CD57− precursors by differentiation occurring in late immune responses

CD3⁺ T cells expressing the 110-kDa CD57 antigen are found in survivors of renal, cardiac and bone marrow transplants, in patients with acquired immune deficiency syndrome and in patients with rheumatoid arthritis. They are also present in normal individuals and expand upon ageing. They do not grow in culture and their role in the immune response is poorly understood. The expression of the various isoforms of the leukocyte common antigen (CD45) identifies a spectrum of differentiation in CD4⁺ and CD8⁺ T cells ranging from naive (CD45RA⁺CD45RB^brightCD45RO^?) through early primed cells (CD45RA^?RB^brightRO^dull) to highly differentiated memory cells which are CD45RA^?RB^dullRO^bright. CD45 isoforms expressed by CD57⁺ T cells showed distinct differences between CD4⁺ and CD8⁺ populations, but in each case indicated an advanced state of differentiation. The expression of T cell receptor Vβ families was highly variable between individuals, but both CD57⁺ and CD57^? cells show a full range of the specificities tested. Vβ expression was more closely related within either the CD4⁺ or the CD8⁺ subsets, irrespective of CD57 expression, than between these subsets, suggesting a relationship between CD57⁺ and CD57^? cells within the same T cell pool. This possibility was supported by experiments showing that CD3⁺CD57⁺ lymphocytes were similar to CD3⁺CD57^? T cells in terms of the production of basic T cell cytokines [interleukin (IL)-2, IL-4, and interferon-γ]. Furthermore, in vitro stimulation of CD3⁺CD57^? T cells in secondary mixed leukocyte reaction or by co-culture with IL-2 and IL-4 induced the appearance of CD3⁺CD57⁺ cells with phenotypic and functional similarities to in vivo CD3⁺CD57⁺ cells. These data strongly suggest that the expression of CD57 is a differentiation event which occurs on CD57^? T cells late in the immune response.     

CD8+ and CD45RA+ human peripheral blood lymphocytes are potent sources of macrophage inflammatory protein 1α, interleukin-8 and RANTES

The chemokines macrophage inflammatory protein 1α (MIP 1α), interleukin-8 (IL-8) and RANTES are potent regulators of leukocyte trafficking. Examination of chemokine secretion by human peripheral blood lymphocytes after stimulation with anti-CD3 or phorbol 12, 13 myristate acetate and ionomycin showed CD8⁺ cells were the dominant source of MIP 1α and RANTES. Although production of MIP 1α and IL-8 were similar in pharmacologically stimulated CD4⁺ CD45RA⁺, CD4⁺ CD45RO⁺, and CD8⁺ CD45RA⁺ cells, the largest amounts of MIP 1α and RANTES were secreted by CD8⁺ CD45RO⁺ lymphocytes. A parallel pattern of prolonged chemokine mRNA expression for at least 18 h after activation was observed in the T cell subsets. These results confirm that human T lymphocytes have a unique capacity for secretion of these three chemokines. In addition, CD8⁺ cells have an unrecognized role in recruiting cells to sites of inflammation, and adult human CD45RA⁺ cells have a physiologically significant secretory capacity.     

Differential expression of type I insulin-like growth factor receptors in different stages of human T cells

Insulin-like growth factor I (IGF-I) has been implicated to play a regulatory role in T cell development and in T cell function. We investigated the expression of type I IGF receptors on human peripheral T cells related to the maturation and activation stage using the type I IGF receptor-specific monoclonal antibody αIR3. It appeared that 87% of the CD4⁺CD45RA⁺ cells and 66% of the CD8⁺CD45RA⁺ cells were αIR3⁺, whereas only 37% of the CD4⁺CD45RO⁺ cells and 38% of the CD8⁺CD45RO⁺ cells bound αIR3. We also found that the fraction of αIR3⁺ cells within in vivo or in vitro activated (HLA-DR⁺) T cells is markedly lower than in nonactivated (HLA-DR^?) cells. In vitro phytohemagglutinin-activated T cells and CD4⁺CD45RO⁺ cells activated with recall antigens also contained less αIR3⁺ cells (1–6%) than nonactivated cells (30–54%).     

C-C chemokines,but not the C-X-C chemokines interleukin-8 and interferon-γ inducible protein-10, stimulate transendothelial chemotaxis of T lymphocytes

Eight chemokines were tested for ability to elicit transendothelial chemotaxis of unstimulated peripheral blood T lymphocytes. The C-C chemokines monocyte chemotactic protein (MCP)-2, MCP-3, RANTES, macrophage inflammatory protein (MCP)-lα, MIP-1β, and, as previously described, MCP-1 induced significant, dose-dependent transendothelial chemotaxis of CD3⁺ T lymphocytes. In contrast, the C-X-C chemokines interleukin-8 (IL-8) and interferon-γ inducible protein-10 (IP-10) failed to induce transendothelial chemotaxis of CD3⁺ T lymphocytes or T lymphocyte subsets. RANTES, MIP-1α, and MIP-1β induced significant transendothelial chemotaxis of CD4⁺, CD8⁺, and CD45RO⁺ T lymphocyte subsets. Phenotyping of mononuclear cells that underwent transendothelial migration to MCP-2, MCP-3, RANTES, or MIP-1α showed both monocytes and activated (CD26 high), memory-type (CD45RO⁺) T cells. Both CD4⁺ and CD8⁺ T lymphocytes were recruited, but not natural killer cells or significant numbers of B cells. MCP-2 was the only C-C chemokine tested that attracted a significant number of naive-type (CD45RA⁺) T lymphocytes. In the absence of endothelium, IL-8 but not IP-10 promoted modest but significant chemotoxis of CD3⁺ T lymphocytes. Our data support the hypothesis that C-C, not the C-X-C chemokines IL-8 or IP-10, promote transendothelial chemotaxis of T lymphocytes.     

Intestinal lymphangiectasia,a disease characterized by selective loss of naive CD45RA+ lymphocytes into the gastrointestinal tract

Intestinal lymphangiectasia (InL) is a disease characterized by hypoproteinemia and lymphocytopenia resulting from blocked intestinal lymphatics and loss of lymph fluid into the gastrointestinal tract. This leads to immunologic abnormalities including hypogammaglobulinemia, skin anergy and impaired allograft rejection. In the present study, we evaluated whether the above immunologic abnormalities are secondary to a quantitative or qualitative disorder of T cells. In initial studies we demonstrated that adult InL patients' peripheral blood contain strikingly (and significantly) reduced numbers of CD4⁺/CD45RA⁺ T cells, whereas the numbers of CD4⁺ / CD45RO⁺ T cells were only moderately (and not significantly) reduced. In addition, the CD4⁺ / CD45RO⁺ T cell population contained an increased percentage of highly differentiated and previously sensitized cells, as demonstrated by decreased CD27 and CD31 expression and increased HLA-DR and CD69 expression. In subsequent functional studies, we showed that the InL CD4⁺ / CD45RO⁺ T cells, when stimulated in vitro, proliferate fivefold less than control CD4⁺ / CD45RO⁺ T cells and produce fourfold more IL-4 and threefold less IFN-γ and IL-2. Thus, this cytokine production profile also reflects the highly differentiated nature of the residual cell population. Overall, these studies provide new information on the trafficking of naive / mature and Th1 / Th2 T cell populations in this disease model.     

Naive and memory T cell infiltrates in chronic hepatitis C: phenotypic changes with interferon treatment

The phenotypes of infiltrating lymphocytes in liver with chronic hepatitis C, including changes associated with interferon (IFN) treatment, were characterized. Specimens obtained from 22 patients treated with IFN were examined using avidin-biotin-peroxidase immunohistochemistry. In areas of lobular and periportal inflammation, most lymphocytes were CD8⁺ T cells of the CD45RO⁺ (memory) subset. The centres of lymphoid follicles were occupied by CD20⁺ B cells and a few CD4⁺ T cells which were CD45RA⁺ (naive subset). Follicular centres were surrounded mainly with CD4⁺ T cells. CD8⁺ T cells, mostly CD45RO⁺, were scattered through the mantle zones of follicles and extended around them. No significant changes in CD45RA⁺ lobular infiltrates accompanied IFN treatment. On the other hand, the number of CD45RO⁺ lobular infiltrates decreased after IFN treatment in complete responders (P <0.01). Moreover, there were significant correlations between CD45RO⁺ cell counts and serum alanine aminotransferase concentrations, CD45RO⁺ cell counts and the liver histologic grade and CD45RO⁺ cell counts and CD8⁺ cell counts. These results suggest that CD8⁺ memory T cells participate in hepatocyte injury in chronic hepatitis C, and that a decrease of CD8⁺ memory T cells correlates with the decreased liver inflammation with IFN treatment.     

Age-related accumulation of LFA-1high cells in a CD8+CD45RAhigh T cell population

The differential expression of CD45 isoforms has been suggested as a marker for stages of post-thymic T cell development, that is, CD45RA+CD45R0^? T cells and CD45RA^?CD45R0⁺ T cells are supposed to be virgin and memory cells respectively. Recently, several adhesion molecules have been shown to be up-regulated on the cell surface of memory T cells, and have been suggested to serve as a memory marker. In this study, we investigated the levels of LFA-1 expression on T cells in various subpopulations defined by CD45 isoform expression in donors of various ages. In CD4⁺ T cells, the proportion of LFA-1^high cells among CD45RA^highCD45R0-T cells remained low in all age groups and did not show significant accumulation with age. CD4⁺CD45RA^?CD45R0^highTcells expressed LFA-1 at a higher level than CD4⁺CD45RA^highCD45R0^? T cells. Thus, the currently prevailing view that CD45RA and CD45R0 can be markers for virgin and primed cells was consistent with LFA-1 expression in CD4⁺ T cell population. In CD8⁺ T cells, however, CD45RA^highCD45R0^? T cells consisted of two distinct subpopulations, LFA-1^low and LFA-1^high cells, whereas CD45RA^?CD45R0^high T cells were almost exclusively LFA-1^high When CD29 expression was examined in place of LFA-1 expression, similar results were obtained; CD45RA^high CD45R0^? T cells consisted of two distinct subpopulations, CD29-^{to low} and CD^29high cells, while CD45RA-CD45R0^high T cells were mostly CD29^high. The proportion of LFA-1^high cells in the CD8+CD45RA^high T cell subpopulation increased significantly as a function of age (r = 0.9, p < 0.001). It ranged from 8% in a 14-year-old donor to 94% in a 79-year-old donor. Furthermore, the proportion of CD8⁺CD45RA^highLFA-1^high cells in the CD8⁺ T cell population increased significantly as a function of age (r = 0.85, p < 0.001). On the other hand, the proportion of LEA-1^high cells in CD8⁺CD45RA^? T cell subpopulation exceeded 90% in most donors irrespective of age. These results indicate that the CD8⁺CD45RA^highCD45R0^? T cell subpopulation contains a considerable number of LFA-1^high cells and CD29^high cells, phenotypically similar to previously activated cells. Thus, in terms of LFA-1 and CD29 expressions, the simple scheme that CD45RA is a marker of virgin cells is not applicable to the CD8⁺ T cell population.     

CCR7+ Central and CCR7− Effector Memory CD4+ T Cells in Human Cutaneous Leishmaniasis

Purpose

The profile of central (=T_CM) and effector (=T_EM) memory CD4⁺ T cell subsets and the possible role as surrogate markers of protection is studied in the volunteers with history of cutaneous leishmaniasis (HCL).

Methods

Profile of T cell subsets based on CCR7/CD45RA expressions and phenotypic changes after soluble Leishmania antigen (SLA) stimulation were analyzed. Then, sorted CD4⁺CD45RO^?CD45RA⁺ naïve T, CD4⁺CD45RO⁺CD45RA^?CCR7^? T_EM, CD4⁺CD45RO⁺CD45RA^?CCR7⁺ T_CM subsets were cultured with SLA for proliferation, cytokine production and intracellular cytokine assays.

Results

In the HCL and control volunteers, the mean frequencies of CD4⁺CD45RA⁺CCR7⁺ naïve T cells and CD4⁺CD45RA^?CCR7^? T_EM cells were higher than the other subsets before culture. Frequency of naïve T cells and CD4⁺CD45RA^?CCR7⁺ T_CM cells was significantly decreased (P?=?0.01 for naïve T and P?<?0.05 for T_CM cells) and frequency of T_EM cells was significantly increased after SLA stimulation compared to before culture (P?<?0.001). By CFSE labeling, CD4⁺CD45RO⁺CD45RA^?CCR7⁺ T_CM cells showed more proliferation potential than CD4⁺CD45RO⁺CD45RA^?CCR7^? T_EM cells. Stimulation of the T_EM cells in HCL volunteers induced a significantly higher IFN-γ production (P?=?0.04) with higher number of intracellular IFN-γ positive cells (P?=?0.032) than the same cells from controls. A significantly higher number of T_CM cells produced IL-2 in HCL volunteers compared with controls (P?<?0.05). Most of the intracellular IFN-γ positive T_EM cells were proliferating CFSE-dim populations (P?<?0.05).

Conclusions

A combination of Leishmania-reactive IFN-γ producing CD4⁺CD45RO⁺CD45RA^?CCR7^? T_EM and Leishmania-reactive IL-2 producing CD4⁺CD45RO⁺CD45RA^?CCR7⁺ T_CM are identified in individuals with history of CL which might play a role in protective recall immune response against Leishmania infection.     

Quantification and phenotype of regulatory T cells in rheumatoid arthritis according to Disease Activity Score-28

Here we studied and characterized different peripheral blood (PB) regulatory T cell (Treg) subsets in rheumatoid arthritis (RA) patients and tested the hypothesis that changes in these cells can be linked to the degree of inflammation and relapsing/remission periods. PB cells were examined from RA subjects (n = 60) with different disease activity score-28 (DAS28) and from healthy controls (n = 40). Frequencies of Treg subsets expressing characteristic membrane antigens, FoxP3 or intracellular cytokines were quantified by flow cytometry. We observed a decrease in the percentages of CD4⁺CD25^high, CD4⁺CD25^int, CD4⁺CD25^int/highFoxP3⁺, CD4⁺CD38⁺, CD4⁺CD62L⁺, CD8⁺CD25^highCD45RA⁺ and CD8⁺CD25^intCD45RA⁺ T cells in PB of RA patients compared to healthy controls. In addition, we found increased percentages of cells expressing membrane/intracellular regulatory antigens such as OX40 (CD134), CD45RB^low or CTLA-4 (CD152), and a higher proportion of other T cell subsets including CD4⁺CTLA-4⁺, CD4⁺IL10⁺, CD4⁺CD25^intIL10⁺, CD4⁺CD25^int TGFβ⁺, CD4⁺CD25^low TGFβ⁺ and CD8⁺CD28^? . We show that most of these changes parallel the intensity of inflammation, with lowest or highest values in patients with moderately/very active disease compared to healthy controls and at times to patients with inactive RA. The balance between these cell subsets and their antigen expression would determine the inflammation levels and could thus be linked to the relapsing/remission periods of the disease.     

Characterizing the immune system after long-term undetectable viral load in HIV-1-infected children

Thirty two HIV-infected children, on highly active antiretroviral therapy (HAART) and >500 CD4⁺ T cells/mm³, were rated according to the time-course of viral load (VL) during the whole follow-up period (>18 months) in a longitudinal retrospective study. (a) uVL group: 15 children with VL below 400 copies/mL; (b) dVL group: 17 children with higher VL. The uVL group showed higher memory (CD4⁺CD45RO⁺) T cells than did dVL group, and higher number of memory activated CD4⁺CD45RO⁺HLA-DR⁺ than did control group (healthy age-matched uninfected children), whereas CD4⁺CD45RA^hi+CD62L⁺ was similar. However, TCR rearrangement excision circles (TRECs) were higher in uVL group than in dVL group. uVL Group showed CD8⁺CD45RO⁺ and CD8⁺CD45RO⁺CD38⁺ higher number than the control group, but lower than the dVL group. The percentage of CD8⁺CD45RA^hi+CD62L⁺, CD8⁺CD45RA⁺, CD8⁺CD62L⁺, and CD8⁺CD28⁺ was higher in uVL group than in dVL group, and lower than in control group. The uVL group showed higher number of activated (HLA-DR⁺CD38⁺, HLA-DR⁺, HLA-DR⁺CD38^–) CD4⁺ T cells and lower percentages of CD4⁺HLA-DR^–CD38⁺ than dVL group. In activated CD8⁺ T cell, the uVL group had lower CD8⁺HLA-DR⁺CD38⁺, CD8⁺HLA-DR⁺, and CD8⁺CD38⁺ than the dVL group. Preeffector (CD8⁺CD57^–CD28^– and CD8⁺CD45RA^–CD62L^–) T cells were lower in the uVL group than in dVL group. In the effector (CD8⁺CD57⁺, CD8⁺CD57⁺CD28^–, and CD8⁺CD45RA⁺CD62L^–) T cells, HIV-infected-children had higher values than control group. HIV-infected-children who respond to HAART had TRECs reconstitution, decreased immune activation, and lower effector CD8⁺ T cells. Moreover, successful HAART allow the increment of activated CD4⁺ T cells.     

Comparison of lymphokine secretion and mRNA expression in the CD45RA+ and CD45RO+ subsets of human peripheral blood CD4+ and CD8+ lymphocytes

Flow cytometric analysis of human peripheral blood T lymphocytes demonstrated that the majority of the CD4⁺ cells were CD29⁺ or CD45RO⁺ “mature” cells while the CD8⁺ cells were primarily CD45RA⁺ “naive” cells. After an initial separation into CD4⁺ and CD8⁺ cells and a secondary separation into CD45 subsets, lymphokine secretion was assessed after phorbol 12-myristate 13-acetate and ionomycin or fixed anti-CD3 stimulation. Within the respective CD45 subsets, CD4⁺ cells produced more interleukin (IL)-2, IL-4, and IL-6; but the CD8⁺ cells secreted more interferon-γ and granulocyte/macrophage-colony-stimulating factor. Tumor necrosis factor-α secretion was similar in the matched CD45 subsets. Northern analysis revealed a parallel pattern of lymphokine mRNA expression in the four lymphocyte subsets. These results suggest that human CD8⁺ peripheral blood lymphocytes have a significant capacity to secrete lymphokines, and that the low lymphokine production observed in unseparated CD8⁺ cells reflects the higher percentage of less functional CD45RA⁺ cells.     

Variation in IL-21-secreting circulating follicular helper T cells in Kawasaki disease

Objective

Circulating follicular helper T (cTfh) cells are a specialized subset of CD4⁺ T cells that express the CXC-chemokine receptor 5 (CXCR5). These cells exhibit immune activities by inducing B cell differentiation and proliferation via the secretion of interleukin (IL)-21. Multiple studies have demonstrated that cTfh cells are associated with the progression and severity of numerous diseases. To investigate the role of cTfh cells in the development of Kawasaki disease (KD), we analyzed the distinct subpopulations of cTfh cells and serum IL-21 levels in different phases of KD.

Methods

According to the differential expression of inducible co-stimulator (ICOS) and programmed cell death protein 1 (PD-1), cTfh cells were divided into distinct subsets. We used flow cytometry and flow cytometric bead arrays (CBA) to analyze subsets of CD4⁺CXCR5⁺ T cells and serum IL-21 levels. The samples were collected from control subjects and Kawasaki disease patients in the acute and remission phases.

Results

In the acute phase (AP), the percentages of ICOS^highPD-1^high, ICOS⁺PD-1⁺, ICOS^?PD-1⁺, CD45RA^?IL-21⁺ cTfh cells and serum IL-21 levels significantly increased. Furthermore, the percentages of ICOS^highPD-1^high and ICOS⁺PD-1⁺ cTfh cells positively correlated with erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) values, whereas the percentage of ICOS^?PD-1⁺ cTfh cells indicated negative correlations. The percentages of ICOS⁺PD-1⁺, ICOS^highPD-1^high and CD45RA^?IL-21⁺ cTfh cells correlated positively with serum IL-21 levels. In the remission phase (RP), the percentages of ICOS^?PD-1⁺, CD45RA^?IL-21⁺ cTfh cells and serum IL-21 levels were significantly decreased. In contrast, the percentages of ICOS⁺PD-1⁺, ICOS^highPD-1^high, and ICOS⁺PD-1^? cTfh cells were further increased. Among these subsets, only CD45RA^?IL-21⁺ cTfh cells correlated positively with serum IL-21 levels.

Conclusions

The present study is the first investigation that examined the distribution of circulating cTfh cell subsets in Kawasaki disease. Both cTfh cells and serum IL-21 are essential to the pathogenesis of KD. Our study provides further understanding of the immune response involved in KD and offers novel insights in the pathogenetic mechanism of this disease.

     

Cytomegalovirus infection induces the accumulation of short-lived, multifunctional CD4+CD45RA+CD27+ T cells: the potential involvement of interleukin-7 in this process

The relative roles that ageing and lifelong cytomegalovirus (CMV) infection have in shaping naive and memory CD4⁺ T-cell repertoires in healthy older people is unclear. Using multiple linear regression analysis we found that age itself is a stronger predictor than CMV seropositivity for the decrease in CD45RA⁺ CD27⁺ CD4⁺ T cells over time. In contrast, the increase in CD45RA⁻ CD27⁻ and CD45RA⁺ CD27⁻ CD4⁺ T cells is almost exclusively the result of CMV seropositivity, with age alone having no significant effect. Furthermore, the majority of the CD45RA⁻ CD27⁻ and CD45RA⁺ CD27⁻ CD4⁺ T cells in CMV-seropositive donors are specific for this virus. CD45RA⁺ CD27⁻ CD4⁺ T cells have significantly reduced CD28, interleukin-7 receptor α (IL-7Rα) and Bcl-2 expression, Akt (ser473) phosphorylation and reduced ability to survive after T-cell receptor activation compared with the other T-cell subsets in the same donors. Despite this, the CD45RA⁺ CD27⁻ subset is as multifunctional as the CD45RA⁻ CD27⁺ and CD45RA⁻ CD27⁻ CD4⁺ T-cell subsets, indicating that they are not an exhausted population. In addition, CD45RA⁺ CD27⁻ CD4⁺ T cells have cytotoxic potential as they express high levels of granzyme B and perforin. CD4⁺ memory T cells re-expressing CD45RA can be generated from the CD45RA⁻ CD27⁺ population by the addition of IL-7 and during this process these cells down-regulated expression of IL-7R and Bcl-2 and so resemble their counterparts in vivo. Finally we showed that the proportion of CD45RA⁺ CD27⁻ CD4⁺ T cells of multiple specificities was significantly higher in the bone marrow than the blood of the same individuals, suggesting that this may be a site where these cells are generated.     

Role of γδ T lymphocytes in the development of Behçet's disease

Phenotypic and functional properties of γδ T cells, which play an important role in mucocutaneous immunity, were examined to elucidate whether immunological abnormality in Behc¸et's disease may be related to a specific T cell population. We found that CD45RA⁺Vγ9⁺Vδ2⁺γδ T cells, which constitute a minor population of γδ T cells in healthy individuals, were increased in number in Behc¸et's disease irrespective of disease activity. This CD45RA⁺ subset of γδ T cells in the active, but not inactive, phase of this disease expressed IL-2Rβ and HLA-DR, suggesting that they are activated in vivo in active Behc¸et's disease. In addition, the CD45RA⁺γδ T cells produced extreme amounts of tumour necrosis factor and contained perforin granules. These data indicate that a phenotypically distinct subset of γδ T cells, CD45RA⁺CD45RO⁻Vγ9⁺Vδ2⁺, may contribute to immunological abnormalities which may lead to complexity of pathophysiology in Behc¸et's disease.     

Reduced Frequency of Memory T Cells and Increased Th17 Responses in Patients with Active Tuberculosis

Phenotypic and functional alterations in Mycobacterium tuberculosis T cell subsets have been reported in patients with active tuberculosis. A better understanding of these alterations will increase the knowledge about immunopathogenesis and also may contribute to the development of new diagnostics and prophylactic strategies. Here, the ex vivo phenotype of CD4⁺ and CD8⁺ T cells and the frequency and phenotype of gamma interferon (IFN-γ)- and interleukin 17 (IL-17)-producing cells elicited in short-term and long-term cultures following CFP-10 and purified protein derivative (PPD) stimulation were determined in noninfected persons (non-TBi), latently infected persons (LTBi), and patients with active tuberculosis (ATB). Phenotypic characterization of T cells was done based on the expression of CD45RO and CD27. Results show that ATB had a reduced frequency of circulating CD4⁺ CD45RO⁺ CD27⁺ T cells and an increased frequency of CD4⁺ CD45RO⁻ CD27⁺ T cells. ATB also had a higher frequency of circulating IL-17-producing CD4⁺ T cells than did LTBi after PPD stimulation, whereas LTBi had more IFN-γ-producing CD4⁺ T cells than did non-TBi. The phenotype of IFN-γ-producing cells at 24 h differs from the phenotype of IL-17-producing cells with no differences between LTBi and ATB. At 144 h, IFN-γ- and IL-17-producing cells were mainly CD45RO⁺ CD27⁺ T cells and they were more frequent in ATB. These results suggest that M. tuberculosis infection induces alterations in T cells which interfere with an adequate specific immune response.     

Differential effect of transforming growth factor-{beta}1 on the activation of human naive and memory CD4+ T lymphocytes

Transforming growth factor-ß1 (TGF-ß1) canhave stimulatory or inhibitory effects on cell growth. For severalcell types, the effect of TGF-ß1 was found to correlatewith the differentiation stage of the cells and the presenceof other cytoklnes. We have studied here the influence of TGF-ß1on CD4⁺ T cell activation in relation to the differentiationstage of the cells by evaluating the effect of TGF-ß1on the prollferatlve responses of purified CD4⁺CD45RA⁺ (unprfmed)and CD4⁺CD45RO⁺ (primed) lymphocytes. Under certain conditions,TGF-ß1 exerted a co-stlmulatory effect on peripheralblood CD4⁺CD45RA⁺ T cells whereas the outgrowth of CD4⁺CD45RO⁺T cells was suppressed in any activation system tested. Theenhancement of prollferatlve responses by TGF-ß1 inTCR/CD3 or CD2 stimulated cultures of CD45RA⁺ cells involvedup-regulatlon of CD25 expression and was dependent on the presenceof exogenous IL-2 or CD28 mAbs; IL-7 driven proliferatlve responseswere suppressed by TGF-ß1. These observations wereconfirmed in experiments with purified cord blood (CB) CD4⁺T cells inasmuch as addition of TGF-ß1 caused a 2-to 7-fold increase in IL-2 driven proliferatlve responses ofthese cells. Finally we show that, in contrast to the effectof TGF-ß1 during primary stimulation of CB CD4⁺ Tcells, TGF-ß1 suppressed T cell proliferation for40% in secondary cultures of these cell. Our findings indicatethat TGF-ß1 Is a blfunctlonal regulator of CD4⁺ Tcell growth in vitro, with co-stimulatory capacities duringCD45RA⁺ T cell mediated primary responses and growth suppresslveeffects during secondary responses of CD45RO⁺ T cells.     

Deficient interleukin-10 production by neonatal T cells does not explain their ineffectiveness at promoting neonatal B cell differentiation

Neonatal T cells are poor promoters of Ig secretion by neonatal B cells. Since IL-10 has been shown to play a role in B cell differentiation, we investigated the relationship of IL-10 production by neonatal T cells and their ability to provide B cell help. Neonatal CD4⁺(CD8⁻) T cells and adult naive CD4⁺ (CD8⁻ / CD45RO⁻) T cells activated with immobilized anti-CD3 produced consistently less IL-10 than adult memory CD4⁺(CD8⁻ / CD45RA⁻) T cells. Production of IL-10 by adult and neonatal T cells was dependent on IL-2, but was unaffected by supplemental IL-4. Despite diminished IL-10 production, supplemental IL-10 increased neonatal T cell-dependent Ig secretion only modestly, but did not increase Ig heavy chain isotype switching. This contrasted with the ability of IL-10 to enhance the secretion of all Ig isotypes by adult B cells stimulated in the presence of either IL-2 or IL-4. These results suggest that IL-10 can promote T cell-dependent Ig secretion but not Ig heavy chain isotype switching by neonatal B cells. However, deficient IL-10 production alone does not account for the poor ability of neonatal T cells to support neonatal B cell Ig production.     

Antigen-independent adhesion of CD4 CD45RA T cells from cord blood

Antigen-independent adhesion of resting adult CD4⁺ CD45RO⁺ T cells to B lymphocytes has been shown to be transient and can be down-regulated by CD4 major histocompatibility complex (MHC) class II molecule interactions. Conversely, adhesion of adult CD4+ CD45RA+ subpopulation to B cells is not regulated by ligands of CD4. We have investigated the regulation of adhesion of cord blood CD45RA⁺ CD4⁺ T lymphocytes. In contrast to adult CD45RA⁺ CD4⁺ T cells, cord blood CD45RA⁺ CD4⁺ T cells were strongly sensitive to the down-regulation of adhesion mediated by the CD4-HLA class II interaction, since adhesion to MHC class II(⁺) B cells was transient and inhibited by an anti-CD4 antibody. In addition, human immunodeficiency virus gpl60, synthetic gpl06-derived peptides encompassing a CD4 binding site inhibited conjugate formation between cord blood CD45RA⁺ CD4+ T cells and B cells. Following activation of the cord blood CD4 T cells by an anti-CD3 antibody, a conversion from a transient to a stable adhesion pattern of cord blood CD4 T cells to B cells occurred in 2 days. The reversal to a transient adhesion occurred at day 8 following anti-CD3 activation in correlation with a complete shift to a CD45RO phenotype of the cord blood CD4 T cells. These data suggest that CD4 T cell adhesion can be developmentally regulated.