Quantitation of lymphocyte subsets by immunofluorescence flow cytometry in idiopathic dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (IDC) is a disease in which immune aberration has been postulated but not confirmed. The frequency of lymphocyte subsets was evaluated in 22 patients with IDC and in 22 blood bank control subjects, using monoclonal antibodies to cell surface markers to allow cell sorting by immunofluorescence flow cytometry. Eighteen patients with heart failure from other causes were also studied. Functional correlations were also made for the natural killer cell subset. Total T-cell frequency, determined with antihuman T (Hybritech), was similar in IDC and control groups: mean 73 ± 12% in IDC patients and 70 ± 9 % in control subjects. B-cell frequency, determined with antihuman la (Hybritech), was also similar: 36 ± 11 % in IDC patients and 31 ± 10% in control subjects. Helper T-cell frequency, identified by OKT4 (Ortho), averaged 47 ± 11 % in IDC and 44 ± 8 % in control subjects (difference not significant). Suppressor/cytotoxic T-cell frequency, established by OKT8, was the same: 28 ± 8 % in IDC and 30 ± 7 % in control subjects, although relative deficiency in suppressor functional activity has been reported in IDC. Helper to suppressor (OKT4/8) ratios, aberrant in many autoimmune diseases, did not differ significantly (IDC 1.9 ± 0.8, control 1.5 ± 0.6). Lymphocyte subsets and OKT4/8 ratio were also similar between IDC and heart failure patients. Natural killer cell frequencies, estimated using 2 antibodies (antihuman Leu-7 and Leu-11, Becton-Dickinson) were the same (9.3 ± 4.9 % in IDC patients, 9.0 ± 4.5 % in control subjects, Leu-7). In contrast, natural killer cell functional activity was decreased in the IDC group; median lymphocyte to target cell (K562 line) ratio resulting in 50% killing (L/T50) was 21 in IDC vs 10.5 in control (p <0.02). Macrophage (OKM1) frequency also did not differ. It is concluded that, despite marked cardiac dysfunction in IDC, relative percentages of lymphocyte subsets, identified by cell surface markers, are not consistently changed. In contrast, functional deficiencies (as for natural killer cells) may be present, suggesting abnormalities in activation that may respond to pharmacologic maneuvers.     

Analysis of subsets of colonic mucosal lymphocyte in ulcerative colitis by two color flow cytometry

To assess how the immunological events occur in the colonic mucosa in patients with ulcerative colitis, it is thought to be important to evaluate the subpopulations and/or subsets of mucosal lymphocytes. In this point of view, we assayed those by lymphocyte isolation techniques and two color flow cytometry. Although our results showed no disease-specific abnormalities of the percentages of CD3, CD4, CD8, CD20, and HLA-DR (+) cells in PBL (peripheral blood lymphocyte) nor CML (colonic mucosal lymphocyte), these subsets of CML appeared to be altered according to the grade of severity of inflammation. In our cases, the HLA-DR (+) cell and CD4 population were larger in severely inflamed mucosa. Furthermore, fluorescence intensities of HLA-DR antigen of CD20 population in CML were greater than those in PBL. These results suggest that the B cell-mediated mechanisms may play an important role in maintaining the severe inflammation, and the clinical significance of these studies are discussed.     

类风湿关节炎并发骨质疏松患者外周血淋巴细胞亚群的表达水平

目的检测类风湿关节炎(rheumatoid arthritis,RA)并发骨质疏松(osteoporosis,OP)患者外周血淋巴细胞亚群的表达水平并探讨其临床意义。方法收集山西医科大学第二医院住院诊治的734例RA患者的基本临床资料、外周血淋巴细胞亚群及骨密度(bone mineral density,BMD)检查结果,根据BMD结果以及是否曾有脆性骨折史将以上患者分为RA未并发OP组551例和并发OP组183例,比较两组临床资料的不同,同时选取81例健康人群作为健康对照组,分析3组外周血淋巴细胞亚群的差异,并对RA并发OP患者行BMD与外周血淋巴细胞亚群间的相关性分析。结果 RA患者OP发生率为24. 93%,其中12. 57%有骨折史。RA并发OP组女性患者比例明显高于未并发OP组(P=0. 021),且年龄较大(61. 85±10. 36 vs. 56. 63±12. 01,P<0. 001),病程更长(7. 17±5. 82 vs. 5. 28±6. 33,P=0. 001),疾病活动相关指标更高(P<0. 05)。相较于健康对照组,RA未并发OP组B细胞水平下降,Th17细胞水平升高,但差异均无统计学意义,Th2细胞及Th17/Treg比值明显升高(P<0. 01),Treg细胞及Th1/Th2比值降低(P<0. 05); RA并发OP组B细胞绝对计数下降(P<0. 05),Th17细胞水平及Th17/Treg比值明显升高(P<0. 01),Treg细胞水平显著下降(P<0. 001)。相较于RA未并发OP组,并发OP组B细胞及Treg细胞水平均明显下降(P<0. 01),Th17细胞水平及Th17/Treg比值升高(P<0. 05)。RA并发OP患者的腰椎BMD与B淋巴细胞和Treg细胞绝对计数及百分计数呈正相关(B淋巴细胞r=0. 290、0. 315; Treg细胞r=0. 318、0. 248,P<0. 05),与Th17细胞绝对计数和百分计数及Th17/Treg比值呈负相关(Th17细胞r=-0. 254、-0. 265; Th17/Treg r=-0. 242,P<0. 05);同样股骨BMD与B淋巴细胞和Treg细胞绝对计数及百分计数也呈正相关(B淋巴细胞r=0. 238、0. 256; Treg细胞r=0. 259、0. 255,P<0. 05),与Th17细胞绝对计数和百分计数及Th17/Treg比值也呈负相关(Th17细胞r=-0. 248、-0. 283; Th17/Treg r=-0. 216,P<0. 05)。结论 RA并发OP患者存在B细胞显著下降和Th17/Treg比例失衡,此与RA患者本身的免疫紊乱密切相关,在RA疾病早期关注免疫微环境并调节其平衡对预防骨质疏松的发生至关重要。     

类风湿关节炎并发骨质疏松患者外周血淋巴细胞亚群的表达水平

目的检测类风湿关节炎(rheumatoid arthritis,RA)并发骨质疏松(osteoporosis,OP)患者外周血淋巴细胞亚群的表达水平并探讨其临床意义.方法收集山西医科大学第二医院住院诊治的734例RA患者的基本临床资料、外周血淋巴细胞亚群及骨密度(bone mineral density,BMD)检查结果,根据BMD结果以及是否曾有脆性骨折史将以上患者分为RA未并发OP组551例和并发OP组183例,比较两组临床资料的不同,同时选取81例健康人群作为健康对照组,分析3组外周血淋巴细胞亚群的差异,并对RA并发OP患者行BMD与外周血淋巴细胞亚群间的相关性分析.结果RA患者OP发生率为24.93%,其中12.57%有骨折史.RA并发OP组女性患者比例明显高于未并发OP组(P=0.021),且年龄较大(61.85±10.36 vs.56.63±12.01,P<0.001),病程更长(7.17±5.82 vs.5.28±6.33,P=0.001),疾病活动相关指标更高(P<0.05).相较于健康对照组,RA未并发OP组B细胞水平下降,Th17细胞水平升高,但差异均无统计学意义,Th2细胞及Th17/Treg比值明显升高(P<0.01),Treg细胞及Th1/Th2比值降低(P<0.05);RA并发OP组B细胞绝对计数下降(P<0.05),Th17细胞水平及Th17/Treg比值明显升高(P<0.01),Treg细胞水平显著下降(P<0.001).相较于RA未并发OP组,并发OP组B细胞及Treg细胞水平均明显下降(P<0.01),Th17细胞水平及Th17/Treg比值升高(P<0.05).RA并发OP患者的腰椎BMD与B淋巴细胞和Treg细胞绝对计数及百分计数呈正相关(B淋巴细胞r=0.290、0.315;Treg细胞r=0.318、0.248,P<0.05),与Th17细胞绝对计数和百分计数及Th17/Treg比值呈负相关(Th17细胞r=-0.254、-0.265;Th17/Treg r=-0.242,P<0.05);同样股骨BMD与B淋巴细胞和Treg细胞绝对计数及百分计数也呈正相关(B淋巴细胞r=0.238、0.256;Treg细胞r=0.259、0.255,P<0.05),与Th17细胞绝对计数和百分计数及Th17/Treg比值也呈负相关(Th17细胞r=-0.248、-0.283;Th17/Treg r=-0.216,P<0.05).结论RA并发OP患者存在B细胞显著下降和Th17/Treg比例失衡,此与RA患者本身的免疫紊乱密切相关,在RA疾病早期关注免疫微环境并调节其平衡对预防骨质疏松的发生至关重要.     

Establishment of nurse-like stromal cells from bone marrow of patients with rheumatoid arthritis: indication of characteristic bone marrow microenvironment in patients with rheumatoid arthritis.

OBJECTIVE: To investigate the microenvironment of bone marrow (BM) of patients with rheumatoid arthritis (RA). METHODS: Nurse cell-like BM stromal cell lines were established from BM mononuclear cells of patients with RA. We examined the various characteristics of these cell lines, including morphology, pseudoemperipolesis activity, cell surface markers, cytokine production and hyaluronan (HA) production. RESULTS: These RA BM nurse cell-like lines (RA-BMNC) were of mesenchymal origin and positive for CD44, CD54 and HLA-DR. They were defined as nurse cells because of pseudoemperipolesis activity that allowed lymphocytes to migrate underneath. RA-BMNC lines produced HA and multiple cytokines including interleukin (IL)-6, IL-7, IL-8 and granulocyte-macrophage colony-stimulating factor (GM-CSF). HA production by BM stromal cells was correlated with pseudoemperipolesis activity. RA-BMNC produced significantly higher levels of IL-6, IL-8 and GM-CSF by co-culture with lymphocytes. The cells also produced IL-1beta, G-CSF and tumour necrosis factor only when co-cultured with lymphocytes. The RA-BMNC maintained the growth of CD14+ myeloid cells unique to severe RA. CONCLUSION: The present results both indicate that RA-BMNC are nurse cells and suggest that they may play an important role in the pathogenesis of RA.     

Phenotypic abnormalities in CD8+ T lymphocyte subsets in patients with rheumatoid arthritis.

We analyzed the cell surface phenotype of CD8+ cells in both peripheral blood and synovial fluid (SF) of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Utilizing the monoclonal antibodies anti-CD45RA, anti-CD29 and anti-S6F1-, one can define both suppressor effector (CD45RA+CD29-S6F1-) and killer effector (CD45RA-CD29+S6F1+) cells within the CD8 population. In patients with OA, normal proportions of CD8+CD45RA+, CD8+CD29+ and CD8+S6F1+ cells were found in both peripheral blood and SF. The peripheral blood of patients with RA, in contrast, showed a decreased percentage of CD8+CD45RA+ cells (13.4 +/- 2.6) (p less than 0.05), but a normal percentage of CD8+CD29+ and CD8+S6F1+ cells. In the SF of patients with RA, we observed a more dramatic decrease in CD8+CD45RA+ suppressor effector cells (6.4 +/- 5.0) (p less than 0.001), a significant increase in killer effector cells as measured by both CD8 + CD29+ (35.5 +/- 9.9) (p less than 0.001) and CD8 + S6F1+ cells (28.2 +/- 11.4) (p less than 0.01). These changes may contribute to the immunologic abnormalities previously noted in this disease and may provide some insight into the pathophysiologic mechanisms of RA.     

Analysis of lymphocyte subsets in the blood of rheumatoid arthritis patients: correlation with disease activity

Various erythrocyte rosette forming cells (ERFC) were quantified in 111 patients with rheumatoid arthritis (RA): total-ERFC (t-RFC), active-ERFC (act-ERFC), autologous-ERFC (auto-ERFC) and high affinity erythrocyte-antibody rosette forming cells (EA-RFC). B lymphocytes were counted using a direct immunofluorescence method. A decrease in act-ERFC and an increase in high affinity EA-RFC was found, but only the levels of the former correlated with the degree of inflammation and may be regarded as an indicator of clinical activity. Conversely, numbers of t-ERFC, auto-ERFC and B lymphocytes were found to be approximately normal. There was no correlation between the level of act-ERFC and the presence of rheumatoid factor, circulating immune complexes or antinuclear antibodies.     

Stimulation of bone marrow erythropoiesis by T lymphocytes of anaemic patients with rheumatoid arthritis.

An inappropriate response of the bone marrow is implicated in the aetiology of the anaemia of chronic disease complicating rheumatoid arthritis. T lymphocyte subsets have been shown to inhibit early erythroid development in vitro in association with some cases of bone marrow failure, and an expanded peripheral blood pool of these cells is reported in rheumatoid arthritis. We have studied the role of peripheral blood T lymphocytes in erythroid bone marrow culture from seven normal volunteers and nine anaemic patients with rheumatoid arthritis and found comparable stimulation of growth in both groups.     

Synovial lymphocyte subsets in rheumatoid arthritis and degenerative joint disease

There is considerable evidence to indicate that the synovitis of rheumatoid arthritis (RA) is immunologically mediated. Recently, it has been postulated that a suppressor-type cell deficiency may play an important role in the pathogenesis of the synovitis. In addition, an immune component may contribute to the synovial alterations in certain examples of degenerative joint disease (osteoarthritis, OA). Using monoclonal antibodies, we evaluated synovial tissue lymphocytes in 12 patients with RA, 2 with juvenile RA, one with adult Still's disease, and 2 patients with OA synovitis in order to delineate the T cell subset patterns. Helper-type cells predominated in 3 patients with RA, while suppressor-type cells were present in equal or greater numbers in 9. The patients with OA showed helper-type cell predominance. Helper-type to suppressor-type cell ratios vary widely in RA synovia which militates against the primacy of the role of a suppressor-type cell deficiency in this disorder. Patients with OA synovitis may display T cell infiltrates comprised mainly of helper-type cells.     

慢性丙型肝炎肝内及周围血淋巴细胞亚群表型分析

目的：机体细胞免疫反应在慢性丙型肝炎中可能起着重要的作用，但是否像乙型肝炎病毒感染那样，丙型病毒（ＨＣＶ）也无肝细胞毒性而是通过机体免疫反应造成肝组织细胞损伤的呢？目前还不完全清楚。方法：为了探索肝内淋巴细胞免疫反应在慢性ＨＣＶ感染中的作用，我们对３６例慢性ＨＣＶ感染病人及６例正常对照应用三色荧光单抗标记流式细胞分析法进行了肝内及周围血淋巴细胞亚群表型测定，并同时应用ＰＣＲ技术进行了血清中ＨＣＶ复制率测定及肝脏组织学检查。结果：周围血中各种淋巴细胞亚群表型在慢性ＨＣＶ感染病人与对照组相似，难以反应ＨＣＶ感染及肝脏损伤情况，而慢性ＨＣＶ感染病人肝内ＣＤ４＋淋巴细胞显著高于对照组，致使肝内ＣＤ４＋／ＣＤ８＋淋巴细胞比率也显著高于对照组（０．５５±０．２１ｖｓ０．２３±０．１２，Ｐ＝０．０４６）。结论：提示ＣＤ４＋Ｔｈ淋巴细胞正性调节ＣＤ８＋Ｔｃ淋巴细胞可能是引起肝细胞损伤的主要原因     

Investigation of platelet glycoprotein IIIa polymorphism using flow cytometry in patients with rheumatoid arthritis

OBJECTIVES: Previous work has shown that the human platelet antigen (HPA) 1b polymorphism of platelet glycoprotein IIIa (GPIIIa) is implicated in the development of ischaemic vascular disease. HPA1b positive platelets have a lower threshold for activation and may exert a greater thrombotic tendency than those without the 1b allele. However, platelets heterozygous for the polymorphism are also more sensitive to aspirin than those homozygous for the 1b allele, which have a similar sensitivity to those without the 1b allele. A flow cytometric method has become available to identify this polymorphism. The aim of our study was to evaluate the use of this assay in patients with rheumatoid arthritis (RA) and to determine the incidence of the 1b allele in these patients. We also compared platelet aggregation and platelet/white blood cell interaction in patients with or without this polymorphism. METHODS: We enrolled 99 patients and measured platelet aggregation in whole blood and platelet-rich plasma (prp), platelet/white blood cell interaction and C-reactive protein (CRP). RESULTS: Thirty-four of the 99 patients were unsuitable for analysis because their baseline expression of GPIIIa was outwith the normal range, making the results outwith the limits of the flow cytometric method. The incidence of the 1b allele in the patients was 29%, with incidence being higher in females, although this failed to reach statistical significance. The number of circulating platelet aggregates and adenosine diphosphate (ADP)-induced aggregation in prp was significantly higher in those patients with the 1b allele. CONCLUSIONS: This method may be of use as an initial screening test.     

Osteoprotegerin expression in bone marrow by treatment with tocilizumab in rheumatoid arthritis

The aim of this study was to investigate histological changes of bone marrow in response to tocilizumab for rheumatoid arthritis (RA). After tocilizumab therapy, bone marrow tissues were extracted from ten RA patients at the time of total knee arthroplasty (TKA). Control samples were obtained from ten RA patients who underwent MTX mono-therapy. Histological examination of structural differences between the tocilizumab and control groups in bone marrow was performed using hematoxylin and eosin (H&E) to evaluate differences. In immunohistochemical examination, the expression of seven molecules including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), CD68, osteoprotegerin (OPG), receptor activator of nuclear kappa B ligand (RANKL), CD4 and osteopontin (OPN) were compared between two groups. NTx was significantly low at 44.5?±?2?nM?BCE/mM?Cr compared with control at 73.2?±?8?nM?BCE/mM?Cr. Immunohistochemical examination revealed that the bone marrow tissues of the RA patients who underwent tocilizumab therapy demonstrated significant positive OPG as compared with the control. However, immunohistochemical examinations after tocilizumab revealed that TNF-α, IL-6, CD68, CD4, OPN and RANKL were not significantly different with control of MTX in bone marrow. Therefore, treatment with tocilizumab increased the expression of OPG as the histological changes with respect to inhibit RANKL-related bone resorption of bone marrow in RA.     

Blood lymphocyte subsets in rats with adjuvant arthritis.

OBJECTIVES--To determine the phenotype of peripheral blood lymphocytes during the time-course of adjuvant arthritis (AA) to detect alterations that could be involved in the pathogenesis of the arthritic process. METHODS--Phenotype analysis was performed on days 7, 14, 21, 28, 42, 56 and 70 after arthritis induction using monoclonal antibodies to CD5, CD4 and CD8 subsets, and flow cytometry. The proportion of activated lymphocytes and lymphocytes was also assessed with monoclonal antibodies to IL-2R (CD25), to Ia antigen and by polyclonal antibodies to rat Ig. RESULTS--Adjuvant arthritis produced leukocytosis with neutrophilia. Rats with AA showed a marked increase in the number of both CD4+ and CD8+ cells. The ratio CD4/CD8 decreased because the rise in CD8+ cells was more pronounced than the increase in CD4+ cells. Changes in lymphocyte counts showed two well-defined periods: the first, from day 14 to day 28, during which the inflammation of the joints reached a maximum and changes in lymphocyte subsets were more pronounced, that is, there was a threefold increase in CD8+ lymphocytes over normal counts, and the second, from day 42 to day 70, in which modified parameters improved considerably but remained different from controls. CONCLUSION--Alterations were detected in the phenotype of peripheral blood lymphocytes in AA, which provides an additional marker of disease activity.     

T cell receptor expression and activation of synovial lymphocyte subsets in patients with rheumatoid arthritis. Phenotyping of multiple synovial sites

Two-color flow cytometry analysis of peripheral blood and synovial lymphocytes from rheumatoid arthritis patients was performed using monoclonal antibodies directed against T cell subsets, T cell activation markers, and T cell receptors. The results showed an abnormally high percentage (greater than 15%) of CD3+, CD4-, and CD8- T cells expressing a specific receptor containing a gamma chain. Phenotypic analysis of lymphocytes infiltrating both knee joints of individual rheumatoid arthritis patients revealed very similar subset distribution and activation levels, despite strong differences in the clinical status between the 2 sites.     

Azathioprine-related bone marrow toxicity and low activities of purine enzymes in patients with rheumatoid arthritis

Objective. Azathioprine (AZA) metabolism largely parallels the endogenous purine pathways. To date, thiopurine methyltransferase (TPMT) deficiency has been reported as a cause of AZA-related bone marrow toxicity in 1 patient with rheumatoid arthritis (RA). We therefore studied purine enzyme activities in 3 patients with RA who experienced AZA-related bone marrow toxicity. Methods. Lymphocyte activity of purine nucleoside phosphorylase and 5′-nucleotidase (5NT) and erythrocyte activity of TPMT, key enzymes in thiopurine catabolism, were measured in 3 RA patients who had experienced AZA-related bone marrow toxicity and in 16 RA patients without signs of toxicity despite at least 6 months of treatment with AZA. Results. Two patients with AZA-related bone marrow toxicity were found to have a TPMT deficiency, 1 partial and 1 total. In the third patient, 5NT activity was found to be well below the lowest level observed in the control subjects. Conclusion. All 3 patients with severe AZA-related bone marrow toxicity had abnormal purine enzyme activities. Deficiency of purine enzymes, including TPMT and 5NT, may be a cause of AZA-related bone marrow toxicity in patients with RA.     

Functional capacities of T lymphocyte subsets from synovial fluid and blood in rheumatoid arthritis.

A reverse haemolytic plaque forming cell (PFC) assay was employed to analyse the impact of T suppressor/cytotoxic and T helper cells on B cell function in 10 patients with rheumatoid arthritis (RA). In all cases T8-enriched cells from synovial fluid and blood suppressed the pokeweed mitogen (PWM) induced IgM, IgG, and IgA secretion by autologous lymphocytes to the same degree. The suppression was partly abolished by irradiation of T8-enriched cells. T4-enriched cells from blood increased the PWM induced Ig secretion by autologous blood B cells. In six of 10 patients responses 1.2 to four times higher were obtained with T4-enriched cells from synovial fluid, but in four of 10 patients synovial fluid T4-enriched cells did not increase the PWM responses of blood B cells. T4- and T8-enriched T cells from synovial fluid comprised more Ia+ cells than did T cells from blood (36% v 3% and 43% v 6%). Ia+ T helper and suppressor/cytotoxic cells may modulate in vivo activation of synovial B cells in RA.     

Methylprednisolone infusion therapy in rheumatoid arthritis patients. The effect on synovial fluid lymphocyte subsets and inflammatory indices

Paired samples of synovial fluid (SF) and blood were obtained prior to and at 4 and 24 hours following high-dose methylprednisolone infusion therapy in a group of patients with refractory rheumatoid arthritis. After therapy there was a significant decrease in numbers of polymorphonuclear leukocytes, lymphocytes, immune complexes, and C-reactive protein in the SF. Measurement of lymphocyte subsets, using monoclonal antibodies, revealed that at 4 hours postinfusion, there was a disproportionate decrease in the percentage of SF lymphocytes expressing class II antigens (HLA-DR or Ia-like). These data suggest that glucocorticoids induce rapid changes in SF indices of disease activity and may directly influence T cell activation within the rheumatoid joint.     

Comparison of blood and synovial fluid lymphocyte subsets in rheumatoid arthritis and osteoarthritis

Summary Immunoregulatory T-cell deficiency is thought to underlie pathogenesis of rheumatoid arthritis (RA) as a systemic autoimmunopathy. The aim of this study was a simultaneous analysis of peripheral blood and synovial lymphocyte subsets (Ly-SS) of RA patients as compared to patients with locally active osteoarthritis (OA). Peripheral blood Ly-SS and paired synovial fluid Ly-SS from 87 RA patients were analysed by two dimensional flow cytometry (Simulset Becton Dickinson) as compared to 15 OA patients. The control group consisted of 32 healthy subjects. The peripheral blood analysis from RA and OA patients revealed a significant decrease of CD8+T-cells and increase of CD4+:CD8+ ratio when compared to the control group. The blood of RA patients showed a significant increase of HLA DR+ and IL 2R+T cells as compared to OA group. The synovial fluid from RA and OA patients showed a significant increase of CD3+, CD8+, HLA DR+ T-cells and decrease of CD4+:CD8+ ratio and CD19+ cells in comparison to the peripheral blood. This study shows, that the OA T-cell system seems not to be activated in peripheral blood in opposition to RA patients. Synovial fluid Ly-SS in OA, however, showed only quantitative but not qualitative differences. OA seems to be mainly a local inflammatory response depending on T-cells, when lymphocyte T activity in blood is diminished.     

Dysregulated lymphocyte proliferation and differentiation in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, inflammatory disease of the synovium of uncertain pathogenesis. A number of phenotypic and functional T-cell defects have been described in RA, including abnormal clonal expansions and suppressed proliferative responses, which suggest a defect in T-cell differentiation. Here, we show that RA patients possess fewer naive CD4(+) T cells than healthy controls. Furthermore, a smaller proportion of these cells contains a T-cell receptor excision circle (TREC). Patients with RA also have unusual populations of T cells. These include immature cells characterized as CD45RB(bright)CD45RA(+)CD62L(-) by flow cytometry and a large population that coexpresses CD45RA and CD45RO. These cells are hyperresponsive to mitogen and TCR stimulation when compared to naive cells. Additionally, an unusual putative central memory subset expressing CD62L, but not CD45RA, appears in RA patients at the expense of more typical cells. Levels of C-reactive protein correlate inversely with the TREC content of naive T cells and positively with the sizes of naive and immature atypical T-cell subsets. These data suggest that inflammation drives proliferation of naive T cells in RA and encourages their differentiation into atypical, hyperresponsive progeny. TREC content of individual naive and atypical T-cell subsets suggests an ontogeny consistent with this hypothesis. These studies provide further evidence of a T-cell differentiation defect in RA, which could explain some of the well-characterized immunologic features of the disease.