Hemodialysis Affects Phenotype and Proliferation of CD4-Positive T Lymphocytes

CD4⁺ T lymphocytes of patients with chronic kidney disease (CKD) are characterized by reduced levels of crucial surface antigens and changes in the cell cycle parameters. Recombinant human erythropoietin (rhEPO) normalizes their altered phenotype and proliferative capacity. Mechanisms leading to the deficient responses of T lymphocytes are still not clear but it is postulated that immunological changes are deepened by hemodialysis (HD). Study of activation parameters of CD4⁺ T lymphocytes in hemodialyzed and predialysis CKD patients could bring insight into this problem. Two groups of patients, treated conservatively (predialysis, PD) and hemodialyzed (HD), as well as healthy controls, were included into the study; neither had received rhEPO. Proportions of main CD4⁺CD28⁺, CD4⁺CD25⁺, CD4⁺CD69⁺, CD4⁺CD95⁺, and CD4⁺HLA-DR⁺ lymphocyte subpopulations and proliferation kinetic parameters were measured with flow cytometry, both ex vivo and in vitro. No differences were seen in the proportions of main CD4⁺ lymphocyte subpopulations (CD4⁺CD28⁺, CD4⁺CD25⁺, CD4⁺HLA-DR⁺, CD4⁺CD69⁺, CD4⁺CD95⁺) between all examined groups ex vivo. CD4⁺ T lymphocytes of HD patients exhibited significantly decreased expression of co-stimulatory molecule CD28 and activation markers CD25 and CD69 after stimulation in vitro when compared with PD patients and healthy controls. HD patients showed also decreased percentage of CD4⁺CD28⁺ lymphocytes proliferating in vitro; these cells presented decreased numbers of finished divisions after 72 h of stimulation in vitro and had longer G0→G1 time when compared to healthy controls. CD4⁺ T lymphocytes of PD patients and healthy controls were characterized by similar cell cycle parameters. Our study shows that repeated hemodialysis procedure influences phenotype and proliferation parameters of CD4⁺ T lymphocytes.     

Defective integration of activating signals derived from the T cell receptor (TCR) and costimulatory molecules in both CD4+ and CD8+ T lymphocytes of common variable immunodeficiency (CVID) patients

CVID is characterized by hypogammaglobulinaemia and impaired antibody production. Previous studies demonstrated defects at the T cell level. In the present study the response of purified CD4⁺ and CD8⁺ T lymphocytes to stimulation with anti-TCR monoclonal antibody (the first signal) in combination with anti-CD4 or anti-CD8, anti-CD2 and anti-CD28 MoAbs (the costimulatory signals) was investigated. Both CD4⁺ and CD8⁺ T cells from the patients showed significantly reduced IL-2 release following stimulation via TCR and costimulation via CD4 or CD8 and CD2, respectively. However, normal IL-2 production following TCR plus phorbol myristate acetate (PMA) costimulation and normal expression of an early activation marker, CD69, after TCR + CD28 stimulation indicated that TCR was able to transduce a signal. Furthermore, both IL-2 and IL-4 release were impaired in CD4⁺ lymphocytes following TCR + CD28 stimulation. In addition, stimulation via TCR + CD28 resulted in significantly decreased expression of CD40 ligand in the patients. These results suggest that the integration of activating signals derived from the TCR and costimulatory molecules is defective in CVID patients; the defect is not confined to costimulation via a single molecule, or restricted to cells producing Thl-type cytokines such as IL-2, and is expressed in both CD4⁺ and CD8⁺T cell subsets.     

Chimaeric anti-CD4 monoclonal antibody cross-linked by monocyte Fcγ receptor mediates apoptosis of human CD4 lymphocytes

Previous studies have shown that murine anti-CD4 monoclonal antibody, cross-linked by rabbit anti-mouse immunoglobulin, could mediate apoptosis of murine CD4⁺ lymphocytes when they were stimulated by T cell receptor antibody. In this study, we have shown that the murine anti-CD4 monoclonal antibody, OKT4, can induce apoptosis in human CD4⁺ T cells stimulated by the recall antigen tuberculin purified protein derivative (PPD) only when cross-linked by rabbit anti-mouse immunoglobulin. The chimeric anti-CD4 monoclonal antibody, cM-T412 whose Fc fragment is human, was able to cause apoptosis without cross-linking by a second antibody. Similarly, abolition of PPD-induced proliferation of peripheral blood mononuclear cells by cM-T412 did not require cross-linking with rabbit anti-human immunoglobulin. Inhibition of proliferation by cM-T412 could be reduced by pre-treating monocytes with heat-aggregated human IgG. This suggested that monocyte Fcγ receptors might be cross-linking the human Fc of cM-T412. Propidium iodide staining together with immunofluorescence showed that the apoptotic cells were indeed CD4⁺ lymphocytes. It is proposed that during treatment with cM-T412 in autoimmune disease such as rheumatoid arthritis, cM-T412-coated CD4 T cells, when they are subsequently stimulated by the unknown arthritogenic antigen, may undergo apoptotic cell death through cross-linking of cM-T412 on Fey receptor-positive cells within the joint.     

CD8+ T cells and not CD4+ T cells are hyporesponsive to CD28- and CD40L-mediated activation in HIV-infected subjects

T cell dysfunction in HIV-infected subjects could be the consequence of altered sensitivity of CD4⁺ or CD8⁺ T cells to various costimulatory signals. Therefore, we studied proliferation and cytokine production in highly purified CD8⁺ and CD4⁺ T cells from HIV-infected and HIV⁻ subjects, induced by co-activation via cell-bound CD80, CD86 and CD40 or by allo-activation. Regardless of the nature of the first and the costimulatory signal, CD8⁺ T cells from patients proliferated consistently less than controls, while responses from CD4⁺ T cells were similar in patients and controls. This phenomenon was observed after ligation of CD28 combined with anti-CD3 or phorbol myristate acetate (PMA), but also after allogeneic stimulation and after activation by CD40 and anti-CD3. Anti-CD3 combined with CD80 or CD86 induced a mixed Th1/Th2-type cytokine profile in both CD4⁺ and CD8⁺ T cells from controls, whereas anti-CD3 plus CD40 induced only low levels of Th2-type cytokines and no interferon-gamma (IFN-γ) in CD4⁺ T cells. Compared with controls, CD4⁺ T cells from patients produced slightly lower levels of IL-10 but equal amounts of IFN-γ, IL-4 and IL-5, while CD8⁺ T cells from patients produced less of all cytokines tested. In conclusion, responses of purified CD4⁺ T cells from HIV⁺ subjects to various costimulatory pathways are relatively intact, whereas CD8⁺ T cells are hyporesponsive at the level of proliferation and cytokine production. A generalized intrinsic CD8⁺ T cell failure might contribute to viral and neoplastic complications of HIV infection.     

Lymphocyte subsets in hemodialysis patients treated with recombinant human erythropoietin

We investigated whether recombinant human erythropoietin (rhEPO) therapy affected the lymphocyte subsets in patients on long-term maintenance hemodialysis (HD) with severe anemia. Before treatment, the numbers of peripheral blood lymphocyte, CD3⁺, CD4⁺, CD8⁺, and CD20⁺ cells were decreased in HD patients compared to those in healthy subjects, while the number of CD3⁺ HLA-DR⁺ cells was increased in HD patients compared to that in healthy subjects. Furthermore, the number of CD4⁺CD45RA⁺ (naive T) cells was markedly decreased in HD patients (112±77 vs 241±146/µl;P<0.01). The number of CD8⁺S6F1⁺ (cytotoxic T) cells in HD patients was also less than that in healthy subjects (247±104 vs 122±83/µl; NS). During a 6-month period of rhEPO therapy, we found that the low level of CD4⁺CD45RA⁺ cells gradually increased (from 112±18 to 163±24/µl;P<0.01) with the elevation of hematocrit values (from 21.5±1.7 to 28.2±3.5%;P<0.05). The number of CD3⁺HLA-DR⁺ cells decreased after 1 month of rhEPO therapy (from 93±14 to 46±13/µl) and gradually declined throughout the 6-month study period. In ourin vitro study, we demonstrated that no effects were observed on [³H]thymidine uptake in the T cell subsets at various concentrations of rhEPO. These results suggest that rhEPO-induced immunoregulation is mediated by an indirect stimulatory effect on the immune system, this stimulation being accompanied by an improvement in physical condition.     

Inflammation, T-Cell Phenotype, and Inflammatory Cytokines in Chronic Kidney Disease Patients Under Hemodialysis and its Relationship to Resistance to Recombinant Human Erythropoietin Therapy

Background Resistance to recombinant human erythropoietin (rhEPO) occurs in some chronic kidney disease (CKD) patients, which may be due to enhanced systemic inflammatory response and to the erythropoiesis-suppressing effect of pro-inflammatory cytokines, some of which are produced by T cells. Aim of study The aim of this study was to investigate the relationship between resistance to rhEPO therapy in hemodialysis CKD patients and inflammatory markers [C-reactive protein (CRP), soluble interleukin (IL)-2 receptor (sIL2R), and serum albumin levels], blood cell counts, T-cell phenotype, cytokine production by T cells, and serum cytokine levels. Materials and Methods We studied 50 hemodialysis CKD patients, 25 responders and 25 nonresponders to rhEPO, and compared them to each other and with 25 healthy controls. When compared to controls, CKD patients showed increased serum levels of CRP, IL-6, and sIL2R and a T-cell lymphopenia, due to decreased numbers of both CD4⁺ and CD8⁺ T cells. T cells from CKD patients had an immunophenotype compatible with chronic T-cell stimulation as shown by the increased percentage of CD28⁻, CD57⁺, HLA-DR⁺, CD28⁻HLA-DR⁺, and CD57⁺ HLA-DR⁺ T cells and produce higher levels of IL-2, INF-γ, and TNF-α after short-term in vitro stimulation, although Th1 cytokines were not detectable in serum. Statistically significant differences were found between responders and nonresponders to rhEPO therapy for total lymphocyte and CD4⁺ T-lymphocyte counts, albumin (lower in nonresponders) and CRP (higher in nonresponders) levels. Conclusion CKD patients under hemodialysis present with raised inflammatory markers and decrease of total lymphocyte and CD4⁺ T-lymphocyte counts when compared with controls. Some of those markers are even further enhanced in nonresponders to rhEPO therapy patients, but resistance to this therapy cannot be justified by a Th1 polarized T-cell response.     

A T cell activation antigen,Ly6C,induced on CD4+ Th1 cells mediates an inhibitory signal for secretion of IL-2 and proliferation in peripheral immune responses

A T cell activation antigen, Ly6C, is considered to be involved in the autoimmunity of some autoimmune-prone mice; however, the function of Ly6C remains largely unknown. We prepared a rat anti-mouse Ly6C monoclonal antibody (mAb) (S14) that inhibits the proliferation of peripheral T cells stimulated with anti-CD3 mAb in vitro. S14 mAb, the specificity of which is confirmed by a cDNA transfectant, recognizes Ly6C antigen preferentially expressed on a part of CD8⁺ T cells in peripheral lymphoid organs. The immunohistochemical analysis demonstrates that Ly6C appears on CD8⁺ T cells in the conventional T cell-associated area of BALB/c but not of nonobese diabetic (NOD) mice, confirming the absence of Ly6C⁺ T cells in NOD mice. Addition of soluble S14 mAb to the culture does not influence the proliferation of T cells in vitro; however, the S14 mAb coated on the plate clearly inhibits the proliferation and IL-2 production of anti-CD3-stimulated peripheral T cells. The T cells are arrested at the transitional stage from G₀/G₁ to S+G₂/M phases, but they are not induced to undergo apoptotic changes in vitro. This inhibitory signal provided through the Ly6C molecule inhibited IL-2 secretion in a subpopulation of the activated CD4⁺ T cells. Ly6C is expressed on T cell clones of both Th1 and Th2 cells, but the cytokine secretion from Th1 clones is preferentially inhibited. These results suggest that Ly6C mediates an inhibitory signal for secretion of cytokines from Th1 CD4⁺ T cells, potentially causing the inhibition of immune response in peripheral lymphoid tissues.     

Ligation of TAPA-1 (CD81) or major histocompatibility complex class II in co-cultures of human B and T lymphocytes enhances interleukin-4 synthesis by antigen-specific CD4+ T cells

We have previously shown that CD4⁺ T cells from allergic individuals are predisposed to producing interleukin (IL)-4 in response to allergens. IL-4 production could be modulated by antigen concentration as well as by the type of antigen-presenting cells (APC), with B lymphocytes inducing greater quantities of IL-4 than monocytes. Using this system we examined IL-4 synthesis after culture of CD4⁺ T cells with B cells, monocytes, or both, as APC in the presence of allergen and a monoclonal antibody against CD81 (TAPA-1), a member of the TM4 superfamily of proteins that regulates activation, proliferation and trafficking of B cells. Addition of anti-CD81 mAb during culture enhanced IL-4 synthesis by 2- to 70-fold over that using an isotype-matched control mAb. Furthermore, anti-CD81 mAb enhanced IL-4 synthesis in CD4⁺ T cells only when CD4⁺ T cells were cultured with B cells but not monocytes as APC, indicating that anti-CD81 mAb affected IL-4 synthesis in T cells via interactions with B cells. However, pretreatment of either population separately with anti-CD81 mAb prior to culture had no effect on subsequent IL-4 synthesis, suggesting a requirement for temporal or cooperative interactions between T and B lymphocytes. In addition, anti-CD81 mAb enhanced IL-4 production but reduced CD4⁺ T cell antigen-specific proliferation, demonstrating that IL-4 production and proliferation by CD4⁺ T cells were inversely related. Finally, mAb to major histocompatibility complex class II but not to anti-CD19 also enhanced IL-4 synthesis when B lymphocytes were used as APC. In all instances, enhancement of CD4⁺ IL-4 synthesis correlated with the presence of large cell aggregates in T-B lymphocyte cocultures. These results indicate that the capacity of B cells to induce IL-4 can be significantly enhanced by ligation of particular molecules on their surface and should aid in the design of treatments for diseases in which modulation of the cytokine profile would be beneficial.     

Costimulation of CD3/TcR complex with either integrin or nonintegrin ligands protects CD4+ allergen-specific T-cell clones from programmed cell death

An optimal stimulation of CD4⁺ cells in an immune response requires not only signals transduced via the TcR/CD3 complex, but also costimulatory signals delivered as a consequence of interactions between T-cell surface-associated costimulatory receptors and their counterparts on antigen-presenting cells ‘APC). The intercellular adhesion molecule-1 ‘ICAM-1, CD54) efficiently costimulates proliferation of resting, but not antigen-specific, T cells. In contrast, CD28 and CD2 support interleukin ‘IL)-2 synthesis and proliferation of antigen-specific T cells more efficiently than those of resting T cells. The molecular basis for this differential costimulation of T cells is poorly understood. Cypress-specific T-cell clones ‘TCC) were generated from four allergic subjects during in vivo seasonal exposure to the allergen. Purified cypress extract was produced directly from fresh collected pollen and incubated with the patients' mononuclear cells. Repeated allergen stimulation was performed in T-cell cultures supplemented with purified extract and autologous APC. The limiting-dilution technique was then adopted to generate allergen-specific TCC, which were also characterized by their cytokine secretion pattern as ThO ‘IL-4 plus interferon-gamma) or Th2 ‘IL-4). Costimulation-induced proliferation or apoptosis was measured by propidium iodide cytofluorometric assay. By cross-linking cypress-specific CD4⁺ and CD8⁺ T-cell clones with either anti-CD3 or anti-CD2, anti-CD28, and anti-CD54 monoclonal antibodies, we demonstrated that CD4+ clones ‘with ThO- or Th2-type cytokine production pattern) undergo programmed cell death only after anti-CD3 stimulation, whereas costimulation with either anti-CD54 or anti-CD28 protects target cells from apoptosis. The costimulation-induced protection from apoptotic death was associated with a significant rise in IL-4 secretion in both Th0 and Th2-type clones. In contrast, cypress-specific Th0 CD8⁺ clones were more susceptible to stimulation-induced apoptosis via either anti-CD3 or anti-CD2, alone or in combination with anti-CD54 or anti-CD28, thus displaying only slight but nonsignificant modifications in the pattern of IL-4 secretion. The death-promoting costimulatory effects were not observed with highly purified normal resting CD4⁺ or CD8⁺ lymphocytes. Taken together, these results suggest that TcR engagement by an allergen in the context of functionally active APC induces activation-dependent cell death of some, perhaps less specific, cells, and this may be an important homeostatic mechanism through which functional expansion of allergen-specific T cells is regulated during an ongoing immune response.     

Human Th1 responses driven by IL-12 are associated with enhanced expression of CD40 ligand

IL- 12 is the prominent inducer of Th1 responses in humans and in the mouse. CD40 ligand (CD40L) plays important roles in regulation of immune responses, including T cell-dependent activation of B cells and cytokine production by monocytes and dendritic cells. The present study examined the influences of IL-12 on the CD40L expression of activated human CD4⁺ T cells. IL-12 enhanced CD40L expression on CD4⁺ T cells stimulated with immobilized anti-CD3 in the complete absence of accessory cells, whereas IL-4 and IL-10 decreased it. Exogenous interferon-gamma (IFN-γ) did not increase CD40L expression on immobilized anti-CD3 stimulated CD4⁺ T cells at any time up to 168 h of culture. The IL-12-induced enhancement of CD40L expression on anti-CD3 activated CD4⁺ T cells was not influenced in the presence of a metalloproteinase inhibitor KB8301, which up-regulated CD40L expression by preventing the processing of membrane-bound CD40L, or B cells, which down-regulated CD40L expression by receptor-mediated endocytosis. These results indicate that IL-12 enhances the CD40L expression of activated CD4⁺ T cells independently of the IFN-γ production. The data thus suggest that Th1 responses induced by IL-12 might play an important role in the regulation of humoral immune responses through up-regulated CD40L expression.     

Increased CD45RO CD62L CD4 T-cell subpopulation responsible for Th2 response in Kimura’s disease

Kimura’s disease is characterized by subcutaneous masses, eosinophilia, and markedly elevated serum immunoglobulin E, suggesting that T helper (Th)2 cells may play a role in the pathogenesis. We investigated Th2 cytokine synthesis by mononuclear cells and possible Th1/Th2 subpopulations in Kimura’s disease. Peripheral blood samples were obtained from seven patients with Kimura’s disease and CD4⁺ T-cell subpopulations separated by CD45RO and CD62L were isolated. Purified cells were stimulated with PHA or anti-CD3 mAb, and the cytokine levels were measured by Cytometric Bead Array kit. Peripheral blood mononuclear cells in the majority of the patients produced Th2 cytokines such as interleukin (IL)-3, IL-4, IL-5, IL-13 or GM-CSF higher than those of controls. The ratio of CD45RO⁺ CD62L⁺ cells in CD4⁺ T cells was increased in six out of seven patients compared to age-matched controls. Especially, patient 1 had remarkably increased levels of CD45RO⁺ CD62L⁺ population in CD4⁺ T cells. In addition, IL-4 production levels by CD45RO⁺ CD62L⁺ CD4⁺ T cells of patients 1 and 2 were higher than those of their CD45RO⁺ CD62L⁻ CD4⁺ T cells, in the same manner as those by a normal control. Taken together, the synthesis of Th2 cytokines and CD62L-positive subpopulation in CD45RO⁺ CD4⁺ T cells, which may represent characteristics of Th2, are increased in patients with Kimura’s disease, suggesting that deviation to Th2 may involve in pathogenesis of the disease.     

Apoptotic cell capture by DCs induces unexpectedly robust autologous CD4+ T‐cell responses

Apoptotic cells represent an important source of self‐antigens and their engulfment by dendritic cells (DCs) is usually considered to be related to tolerance induction. We report here an unexpectedly high level of human CD4⁺ T‐cell proliferation induced by autologous DCs loaded with autologous apoptotic cells, due to the activation of more than 10% of naive CD4⁺ T cells. This proliferation is not due to an increase in the costimulatory capacity of DCs, but is dependent on apoptotic cell‐associated material processed through an endo‐lysosomal pathway and presented on DC MHC class II molecules. Autologous CD4⁺ T cells stimulated with apoptotic cell‐loaded DCs exhibit suppressive capacities. However, in the presence of bacterial lipopolysaccharide, apoptotic cell‐loaded DCs induce the generation of IL‐17‐producing cells. Thus, apoptotic cell engulfment by DCs may lead to increased autologous responses, initially generating CD4⁺ T cells with suppressive capacities able to differentiate into Th17 cells in the presence of a bacterial danger signal such as LPS.     

Secretion of the eosinophil-active cytokines interleukin-5, granulocyte/macrophage colonystimulating factor and interleukin-3 by bronchoalveolar lavage CD4+ and CD8+ T cell lines in atopics asthmatics,and atopic and nonatopic controls

Specific eosinophil accumulation and activation within the asthmatic bronchial mucosa are thought to occur at least partly through the actions of cytokines, including interleukin (IL)-5, IL-3 and granulocyte/macrophage colonystimulating factor (GM-CSF). Although mRNA encoding some of these cytokines has been demonstrated in bronchoalveolar lavage (BAL) fluid cells and bronchial biopsies from asthmatics, it has yet to be established whether these cells produce the translated products and whether expression is associated with CD4⁺ T helper or CD8⁺ cytotoxic T cells. We addressed this problem by raising polyclonal CD4⁺ and CD8⁺ T cell lines from the BAL fluid of six atopic asthmatics, five atopic non-asthmatics and seven non-atopic non-asthmatic controls. BAL fluid cells obtained at fiberoptic bronchoscopy were depleted of adherent cells, and then T lymphocytes expanded by stimulation with monoclonal anti-CD3 antibody and recombinant human IL-2. When lymphocytes had expanded to sufficient numbers, CD4⁺ and CD8⁺ cells were separated by positive selection with magnetic beads coated with anti-CD4 or anti-CD8 monoclonal antibodies and further expanded. Cytokine secretion by standardized cell numbers was measured by enzyme-linked immunosorbent assays. BAL CD4⁺ T cell lines from the asthmatics secreted significantly elevated quantities of both IL-5 and GM-CSF as compared with lines from the atopic and non-atopic controls (p = 0.023–0.003). In contrast, IL-3 secretion did not significantly differ between the groups. In some subjects, CD8⁺ T cell lines also secreted significant quantities of these cytokines and there was a trend for IL-5 secretion by these cells to be higher in asthmatics than non-atopic controls (p = 0.035). These data are consistent with the hypothesis that activated T lymphocytes from asthmatics, particularly of the CD4⁺ subset, are predisposed to release elevated quantities of cytokines relevant to the accumulation and activation of eosinophils.     

Reversal of the inhibitory effects of HIV-gp120 on CD4+ T cells by stimulation through the CD28 pathway

The effects of exposure to HIV-gp120 on proliferation and cytokine production by T cell lines were investigated. T cell lines were generated by stimulation of peripheral blood mononuclear cells from several healthy donors with cross-linked anti-CD3 antibodies and IL-2. These T cell lines exhibited the characteristics of Th1 cells, producing IL-2 and interferon-gamma (IFN-γ), but not IL-4, on stimulation with anti-CD3 antibodies. In the presence of gp120, stimulation with anti-CD3 antibodies was inhibited in terms of both proliferative responses and the secretion of IL-2 and IFN-γ. Similar effects were observed when a T cell line was stimulated in the presence of a synthetic peptide representing the CD4-binding region of gp120. Neither gp120 nor the CD4-binding region peptide had any effect on IL-4 production by the T cell lines. Stimulation through the CD28 pathway partially restored both the proliferative effect and cytokine production by T cell lines in response to anti-CD3 antibodies in the presence of gp120. Anti-CD28 antibodies also partially restored cytokine production when purified CD4⁺ T cells from a T cell line were stimulated with anti-CD3 antibodies in the presence of gp120. Anti-gp120 antibodies partially or completely reversed the inhibitory effects of gp120 on T cell proliferation. These results indicate that stimulation through the CD28 pathway may restore defective CD4⁺ T cell responses in HIV-infected individuals.     

CD30 cell expression and abnormal soluble CD30 serum accumulation in Omenn's syndrome: Evidence for a T helper 2-mediated condition

Omenn's syndrome (OS) is a severe immunodeficiency, characterized by clinical and laboratory features reminiscent of a T helper type-2 (Th2) response. CD30, a member of the tumor necrosis factor receptor superfamily, has been found to be preferentially expressed by human T cell clones exhibiting a Th2-like profile and function. We investigated whether there are derangement in CD30 expression in tissues, and/or abnormalities in soluble CD30 (sCD30) levels in the serum, or both, of three children with OS and one child with maternal engraftment and Omenn's-like syndrome (OLS). Large proportions of tissue-infiltrating T lymphocytes from all four patients expressed CD30, whereas in control tissues, including peripheral blood, CD30⁺ T lymphocytes were extremely few or absent. In addition, levels of sCD30 were abnormally increased in all patients' sera. T cell clones were generated from sorted CD30⁺ and CD30^? peripheral blood T cells of the patient with OLS who showed unusually high numbers of circulating CD30⁺ T lymphocytes. Most CD4⁺ T cell clones derived from CD30⁺ cells showed a Th2-like cytokine profile, whereas the majority of clones generated from CD30^? T cells were Th1. These findings support the hypothesis that Th2 cells are involved in the pathogenesis of OS. Moreover, they provide evidence that detection of CD30⁺ T cells in tissues, increased levels of sCD30 in biological fluids, or both, reflect the presence of immune responses characterized by prevalent activation of T cells producing Th2 cytokines.