Abnormal interleukin-7 function in common variable immunodeficiency

Common variable immunodeficiency (CVID) is characterized by low levels of circulating immunoglobulins, leading to frequent infections, particularly of the respiratory tract. Frequently, T-cell abnormalities are observed. Interleukin-7 (IL-7) is involved in the homeostasis of lymphocytes, and may be elevated in lymphopenia. Mutations of genes related to IL-7 may lead to severe immunodeficiency disorders. We report elevated plasma levels of circulating IL-7 in a subgroup of CVID. These patients have increased numbers of circulating CD8+ T cells with decreased apoptosis and a predominance of CC chemokine receptor 7- (CCR7-) effector-memory T cells. Moreover, in some of these patients there is impaired response to IL-7 as assessed by in vitro proliferation and secretion of interferon gamma and transforming growth factor beta. These findings suggest novel pathogenic mechanisms and specific targets for further research in CVID.     

Elevated levels of activated CD4 T cells in common variable immunodeficiency: association with clinical findings

BackgroundCommon variable immunodeficiency (CVID) is a very heterogeneous syndrome defined by impaired immunoglobulin production. The primary defect remains unknown, but many reports describe peripheral blood T and B lymphocyte dysfunctions in a substantial proportion of CVID patients. Immunophenotypic alterations on memory B lymphocytes correlate with clinical findings. A B-cell-oriented classification principle of the patients has been proposed.Methods and resultsWe investigated the expression of activation surface molecules on CD4 and CD8 T-cells from 14 patients with CVID, 6 non-CVID hypogammaglobulinemic patients with recurrent infections, 47 asymptomatic HIV-positive patients without AIDS defining conditions and 23 healthy subjects. Lymphocyte subsets were analysed by three-colour flow cytometry. Monoclonal panel: CD38-FITC/HLADR-PE/CD4 or CD8-PerCP. In CVID patients serum levels of CD4 T-cells co-expressing the activation marker HLA-DR [CD4 + DR + (34 %), CD4 + CD38 + DR + (18 %)] were significantly elevated compared with controls. Significant increases in CD8 + DR + (54%), CD8 + CD38 + (43 %) and CD8 + CD38 + DR + (29 %) T-cells were observed in comparison with healthy controls. CVID patients with splenomegaly, lower pre-infusion IgG levels (< 600 mg/dl), autoimmune or lymphoproliferative conditions demonstrated even higher levels of CD4 + CD38 + DR + T cells (22, 22, 21 and 21 % respectively) compared with other CVID patients (13, 13, 15 and 15 % respectively).ConclusionThese findings indicate a state of ongoing T lymphocyte activation which is associated with clinical findings frequently observed in CVID.     

T and B lymphocyte abnormalities in bone marrow biopsies of common variable immunodeficiency

In common variable immunodeficiency (CVID) defects in early stages of B-cell development, bone marrow (BM) plasma cells and T lymphocytes have not been studied systematically. Here we report the first morphologic and flow cytometric study of B- and T-cell populations in CVID BM biopsies and aspirates. Whereas the hematopoietic compartment showed no major lineage abnormalities, analysis of the lymphoid compartment exhibited major pathologic alterations. In 94% of the patients, BM plasma cells were either absent or significantly reduced and correlated with serum immunoglobulin G levels. Biopsies from CVID patients had significantly more diffuse and nodular CD3(+) T lymphocyte infiltrates than biopsies from controls. These infiltrates correlated with autoimmune cytopenia but not with other clinical symptoms or with disease duration and peripheral B-cell counts. Nodular T-cell infiltrates correlated significantly with circulating CD4(+)CD45R0(+) memory T cells, elevated soluble IL2-receptor and neopterin serum levels indicating an activated T-cell compartment in most patients. Nine of 25 patients had a partial block in B-cell development at the pre-B-I to pre-B-II stage. Because the developmental block correlates with lower transitional and mature B-cell counts in the periphery, we propose that these patients might form a new subgroup of CVID patients.     

Characterization of common variable immunodeficiency: identification of a subset of patients with distinctive immunophenotypic and clinical features

The peripheral blood lymphocyte surface markers and clinical features of 38 patients with common variable immunodeficiency (CVID) were assessed. These studies identified a subset of CVID consisting of 14 of the 38 patients with a distinctive T-cell immunophenotype and clinical findings. The phenotypic changes were characterized by an abnormally low CD4/CD8 ratio (less than or equal to 0.9) due primarily to a significant increase in CD8 T cells. In addition, there was an expansion in CD8 T cells coexpressing CD57 and increased expression of the activation markers HLA-DR and interleukin-2 receptor (IL-2R) by these cells. This group of immunophenotypically abnormal CVID patients also had characteristic clinical features, including splenomegaly (P less than .02) and in vivo T-cell dysfunction based on the evaluation of delayed-type hypersensitivity (P less than .05). Approximately 71% of these patients had splenomegaly and 42% were anergic in contrast to the remaining group of CVID patients, in which 29% had splenomegaly and 7% were anergic. These findings define a subgroup of CVID patients that have specific immunophenotypic features and functional T-cell abnormalities.     

Immunophenotypic profile of T cells in common variable immunodeficiency: is there an association with different clinical findings?

BackgroundA system based on the B-cell phenotype has recently been proposed to classify patients suffering from common variable immunodeficiency (CVID). Immunophenotypic T-cell abnormalities have also been correlated with clinical findings, although they have never been used in classification strategies.ObjectiveTo simultaneously assess T and B-cell subset abnormalities in CVID patients and their relationship with clinical findings. To identify potential immunophenotypic T-cell abnormalities that could be further evaluated in multicenter studies.Patients and MethodsPeripheral blood lymphocytes from 21 CVID patients and 21 healthy donors were stained for T and B-cell subsets, analyzed by flow cytometry, and correlated with clinical characteristics.ResultsPatients classified as MB0 (CD19/CD27+ < 11 %) showed higher percentages of CD4/CD45RA? (87 % vs 67 %, p = 0.028) and lower percentages of CD8/CD45RA+CCR7+ (10 % vs 26 %, p = 0.028) and CD4/CD25+ T-cells (36 % vs 62 %, p = 0.034) than MB2 patients. Even though our cohort was small, we observed a higher prevalence of distinct clinical complications of CVID in patients with B and T-cell abnormalities. Nonmalignant lymphoproliferative disorders and IgG hypercatabolism were more frequently observed in MB0 patients. A higher prevalence of splenomegaly was observed among CVID patients with increased levels of CD4/CD45RA?, activated CD4/CD38+DR+, CD8/DR+, and CD8/CD38+ T-cells, as well as in those with lower percentages of CD4/CD45RA+CCR7+ and CD4/CD25+ T-cells. Lymphoproliferative disorders were more prevalent among CVID patients with higher CD4/CD45RA? percentages.ConclusionThe study of T-cell subsets warrants further evaluation as a potential tool to better identify CVID patients with distinct clinical profiles.     

Common variable immunodeficiency. Old questions are getting clearer

Common variable immunodeficiency (CVID) is a heterogeneous entity characterized by an impaired ability to produce antibodies. The failure is localized in partially mature B lymphocytes, though T lymphocyte abnormalities are occasionally present. This deficiency affects antibody synthesis and class switch from IgD and IgM, to IgG and IgA. CVID is related to selective IgA deficiency, and both abnormalities may coincide in one same family, and evolve from one to another in the same patient. The symptoms generally manifest in adults, but can occur at any age, even in infancy. Recurrent bacterial infections or pneumonias are frequent, and may be complicated by gastrointestinal problems, granulomas, autoimmune disorders or malignancies. A defect in memory B cells seems to condition the clinical severity. Recently, several mutations in genes encoding for molecules (CD19, TACI, ICOS) involved in B cell survival and isotype switch have been identified in patients with CVID. Nevertheless, genetic abnormalities have been found in less than 25 % of cases with CVID; the underlying mechanism thus remains unknown in the majority of CVID patients, and research in this field must continue.     

Effect of diet and age on jejunal and circulating lymphocyte subsets in children with coeliac disease: persistence of CD4-8-intraepithelial T cells through treatment.

Monoclonal antibodies were used to determine the relative numbers of T lymphocyte subsets in 61 jejunal biopsies and in peripheral blood of 35 children with coeliac disease, and of 13 healthy controls. The T cell numbers in the lamina propria were unaffected by a change from gluten-free to gluten containing diet in the patients. The number of intraepithelial lymphocytes (where the CD8 cells predominated) were significantly raised in patients taking gluten. Ten to 20% of the patients' intraepithelial CD3 (mature T) cells expressed neither CD8 nor CD4 surface antigens. This CD4 8 T cell population persisted through gluten elimination and challenge. The circulating lymphocyte subsets showed little variation with the diet although there was a marked increase in the proportion (14.9%) of CD4 8 T cells in patients during gluten elimination. In the histologically normal jejunal mucosa from control subjects, the age of the subject showed a positive correlation with villus intraepithelial CD3+ and CD8+ cells, and crypt intraepithelial CD4+ cells. No clear cut effect of age was observed on lamina propria lymphocyte counts of the controls, or on the lymphocyte counts in jejunal mucosa of the coeliac patients. The observed CD3+4-8- lymphocytes may represent activated cells unable to present their surface antigens, or they may be gamma delta-receptor bearing T cells, which could have a significant role in the pathogenesis of coeliac disease.     

Analysis of class-switched memory B cells in patients with common variable immunodeficiency and its clinical implications.

BACKGROUND: Common variable immunodeficiency (CVID) comprises a heterogeneous group of primary immunodeficiency disorders characterized by hypogammaglobulinemia leading to recurrent infections. Some patients with CVID are more susceptible to earlier onset of respiratory disease and bronchiectasis. It has been suggested that memory B cells, characterized by CD27 expression, can be used as a means to classify subsets of CVID patients. OBJECTIVE: The aim of this study was to classify a sample of Iranian patients with CVID by quantification of peripheral blood memory B cells and immature B cells and to assess the relationship between this classification and the clinical characteristics of the patients. METHODS: The study included 29 patients with CVID and 20 healthy controls. Patients were grouped as follows, according to the quantification of peripheral memory B cells: group I had less than 0.4% switched memory B cells (CD27+, immunoglobulin [Ig] M-, IgD-) in peripheral blood lymphocytes (PBL), while in group II switched memory B cells represented more than 0.4% of PBL. Group I patients were further subdivided into groups Ia and Ib according to the proportion of CD21- peripheral B cells. The clinical and laboratory findings for the patients were then compared among the 3 groups. RESULTS: The percentage of switched memory B cells (CD27+IgM-IgD- cells in peripheral B lymphocytes) was markedly reduced in CVID patients compared with controls (P < .001). This percentage was less than 0.4% (group I) in 20 patients (69%) (P < .05). In the remaining 9 patients (group II) and all healthy controls, the percentage was greater than 0.4%. Bronchiectasis was more frequent in group I than group II (P < .05). Following subdivision of group I patients into groups Ia and Ib based on CD21 peripheral B cells, the rate of autoimmunity was found to be much higher in group Ia than group Ib. CONCLUSIONS: CVID patients with reduced numbers of switched memory B cells are more prone to recurrent respiratory infections and development of bronchiectasis, and as such, need more special care than other CVID patients. Thus, classification of CVID patients by assessment of switched memory B cells could help physicians to predict clinical prognosis of these patients.     

Low percentages of regulatory T cells in common variable immunodeficiency (CVID) patients with autoimmune diseases and its association with increased numbers of CD4+CD45RO+ T and CD21low B cells

BackgroundCommon variable immunodeficiency (CVID) is a heterogeneous group of primary antibody deficiencies defined by marked reductions in serum IgG, IgA and/or IgM levels and recurrent bacterial infections. Some patients are associated with defects in T cells and regulatory T cells (Tregs), resulting in recurrent viral infections and early-onset autoimmune disease.MethodsWe analyzed whether there is an association between Tregs cells (CD4+CD25+CD127^low and CD4+CD25+FoxP3+); memory T cells (CD4+CD45RO+); memory B cells (CD19+CD27-IgD-); and CD21^low B cells (CD19+CD38^lowCD21^low); as well as autoimmune manifestations in 36 patients with CVID (25 women and 11 men, mean age 24 years), all by flow cytometry.ResultsFourteen patients presented with autoimmune diseases (AI) (39%), including 11 with autoimmune thrombocytopenia (ITP) (31%); two with vitiligo (6%); one with systemic lupus erythematosus (LES) (3%); and one with multiple sclerosis (MS) (3%). CVID patients with AI had a reduced proportion of Tregs (both CD4+CD25+CD127^low and FoxP3+ cells) compared with healthy controls. CVID patients with AI had expanded CD21^low B cell populations compared with patients who did not have AI. A correlation between increased CD4+CD45RO T cell populations and reduced Tregs was also observed.ConclusionsOur results showed that 39% of patients with CVID had AI and reduced Tregs populations. Research in this area might provide noteworthy data to better understand immune dysfunction and dysregulation related to CVID.     

Abnormalities of T cell immunoregulation in hemorrhagic fever with renal syndrome

The functions of spontaneous suppressor T cells and T lymphocyte subsets in patients with hemorrhagic fever with renal syndrome were compared. In the early stages of disease, decreased activity of spontaneous suppressor T cells was concurrent with increased numbers of CD8+ cells and a reversed CD4:CD8 ratio. These changes were related to abnormalities in serum C3 level and circulating immune complexes. In the recovery stages of the illness, spontaneous suppressor T cell activity and T cell subsets returned to normal levels.     

Autoimmune and Lymphoproliferative Complications of Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is frequently complicated by the development of autoimmune and lymphoproliferative diseases. With widespread use of immunoglobulin replacement therapy, autoimmune and lymphoproliferative complications have replaced infection as the major cause of morbidity and mortality in CVID patients. Certain CVID complications, such as bronchiectasis, are likely to be the result of immunodeficiency and are associated with infection susceptibility. However, other complications may result from immune dysregulation rather than immunocompromise. CVID patients develop autoimmunity, lymphoproliferation, and granulomas in association with distinct immunological abnormalities. Mutations in transmembrane activator and CAML interactor, reduction of isotype-switched memory B cells, expansion of CD21 low B cells, heightened interferon signature expression, and retained B cell function are all associated with both autoimmunity and lymphoproliferation in CVID. Further research aimed to better understand that the pathological mechanisms of these shared forms of immune dysregulation may inspire therapies beneficial for multiple CVID complications.     

Lymphocyte kinetics and precursor frequency-dependent recovery of CD4(+)CD45RA(+)CD62L(+) naive T cells following triple-drug therapy for HIV type 1 infection

New therapeutic regimens have dramatically altered morbidity and mortality attributed to HIV-1 infection. Changes in lymphocyte subsets after treatment may mirror salutary clinical changes. Over 4 months we analyzed lymphocyte subsets in 20 patients starting new HIV-1 therapy. Absolute numbers of lymphocytes, CD4+ T cells, CD8+ T cells, and B cells increased significantly by 4 months, but CD8+ T cell and B cell increases were restricted to late-stage patients. Subset analysis revealed that the magnitude of recovering naive-phenotype CD4+ T cells (slope) correlated with the number of these cells present at baseline, equaling or exceeding the memory-phenotype slope within days if these naive cells were abundant at baseline. Five of 10 patients in whom naive-phenotype CD4+ T cells were absent at baseline partially repopulated these cells by 4 months. These findings have important implications for the origin and mechanisms of renewal of naive-phenotype CD4+ T cells following effective treatment for HIV-1 infection.     

Gastrointestinal Manifestations in Patients with Common Variable Immunodeficiency

This study focuses on endoscopic and pathologic alterations of gastrointestinal (GI) disorders of Iranian patients with common variable immunodeficiency (CVID). Nineteen of 39 CVID patients (48%) had GI complaints. The most common symptom was chronic diarrhea (28%). In endoscopic examination of small intestines, 15 patients had no abnormal finding. Duodenal biopsy revealed villous atrophy in eight and nodular lymphoid hyperplasia in three patients. There was no statistically significant difference between patients with and patients without duodenal villous atrophy regarding the presence of chronic diarrhea, anemia, and absolute CD4+T cells. In three patients, biopsies of the colon showed chronic noncrypt-destructive colitis. GI problems pose a high morbidity to CVID patients and are second only to respiratory complications. CVID patients are at increased risk of infectious and inflammatory conditions in the GI tract. Early diagnosis of these complications improves the quality of life and well-being of patients.     

Abnormalities in lymphocyte profile and specificity repertoire of patients with Waldenstrom's macroglobulinemia, multiple myeloma, and IgM monoclonal gammopathy of undetermined significance

The characteristics of T and B lymphocyte profile and B lymphocyte specificity repertoire were compared in patients with Waldenstrom's macroglobulinemia (WM), IgM monoclonal gammopathy of undetermined significance (IgM MGUS), multiple myeloma (MM), and age-matched normal subjects. Patients with MM had both significantly reduced frequency and number of sIg+ (surface Ig) B cells, whereas patients with WM and IgM MGUS had a reduced frequency but normal numbers of sIg+ B cells in circulation as detected in a capping assay. WM was distinguished by the large numbers of cells in the peripheral blood lymphocyte (PBL) pool that expressed CD9 (BA-2) and CD24 (BA-1) and were monoclonal, based on light chain analysis using flow cytometry. The profile of T lineage cells showed that the ratio of CD4:CD8 was significantly reduced in both MM and WM due to a reduction in the CD4 set. The CD4+ cells were qualitatively abnormal as well, with an enriched proportion of the 4B4+ (CDw29) subset and decreased proportion of the Lp220+ (CD45R) subset. This appeared to be an effect of the disease process on the relatively immature Lp220+ set. From clonal analysis, those patients with WM or IgM MGUS (unlike MM patients) did not exhibit enhanced reactivity with auto-Ig determinants, and most WM patients (7/8) and half of the IgM MGUS patients (3/6) did not have enriched proportions of B cells reactive to tetanus toxoid (TT). The TT-specific B cells in both WM and IgM MGUS, in contrast to MM, appeared fully functional in secretion of anti-TT IgM in vivo. We speculate that the more severe immunodeficiency in MM may be controlled or exacerbated by the presence of an anti-Ig network. The absence of this network in WM allows a relatively more effective immune response, but the immunodeficiency that is observed in these patients involves some abnormality in normal lymphocyte differentiation (is also present in MM).     

CD5+ B lymphocytes and other lymphocyte subsets in primary Sj?gren's syndrome.

CD5+ B cells and other lymphocyte subsets were analyzed by flow cytometry in patients with primary Sj?gren's syndrome (pSS), in healthy subjects (HS) and in patients with various control diseases. When compared with HS, patients with pSS were found to have similar levels of CD5+ B cells and decreased levels of CD8+ T cells (P = 0.0003). When compared with patients with various other diseases, however, the number of CD5+ B cells in pSS was more than twice as high (P = 0.0002), whereas no difference was found between numbers of CD8+ T cells. When the number of CD5+ B cells was expressed as a percentage of total B cells, the results obtained were similar to those with absolute numbers. Determination of lymphocyte subsets may be used as a diagnostic aid for Sj?gren's syndrome in selected patients with suspected immunological diseases of unknown type.     

Lymphocytes and B-cell abnormalities in patients with common variable immunodeficiency (CVID)

Background and aimsCommon variable immunodeficiency (CVID) is a primary antibody deficiency characterised by decreased antibody production and low or normal B-cell numbers. To elucidate the clinical and immunological heterogeneity of CVID, we studied 16 patients diagnosed with CVID.MethodsWe analysed B, T and NK cell populations. We also assessed CD27 expression to define B-cell subsets and examined the expression of molecules important in B-cell proliferation and differentiation, such as the transmembrane activator and CALM interactor (TACI), inducible costimulator (ICOS), CD154 and CD40.ResultsWe observed reduced B and T-cell numbers in CVID patients; this reduction was more pronounced in adults. While one group of patients (group I) showed a significant reduction in CD27+ memory B-cells, another group (group II) of patients exhibited numbers of CD27+ memory B-cells similar to the healthy donor. The frequency of B-cells and T-cells expressing CD40 and ICOS, respectively, was significantly lower in all CVID patients compared with healthy donors. Finally, a correlation between the frequency of CD27+ memory B-cells and clinical features was observed in CVID patients.ConclusionThese results suggest that in some patients, the combined defects in both T and B-cells may account for CVID. Additionally, patients in group I exhibited an increased frequency of pneumonia and chronic diarrhoea.     

Phenotypic and clonal analysis of T lymphocytes in childhood immune thrombocytopenic purpura

In an attempt to identify and characterize T-lymphocyte immunoregulatory abnormalities in immune thrombocytopenic purpura (ITP), we have performed phenotypic and clonal analysis on peripheral T lymphocytes from 23 children with ITP. Quantitation of lymphocyte subpopulations showed that children with acute ITP had higher numbers of CD45RA+ and lower numbers of CD45RO+ T cells than children with chronic ITP or controls, but these differences may be age related. Analysis of T-cell receptor variable beta gene usage identified 2 boys with chronic ITP and elevated numbers of V beta 8+ T cells. Eight T- cell clones were established (6 CD4+, 4B4+ helper-inducer lines and 2 CD8+ lines) that showed in vitro proliferation against allogeneic platelets. The addition of autologous antigen-presenting cells enhanced the proliferation of six clones, but not for two clones that coexpressed natural killer (NK) markers. Four of seven positive clones also had measurable interleukin (IL)-2 secretion following platelet stimulation, providing further evidence for T-cell reactivity. Our results provide the first evidence that patients with ITP may have platelet-reactive T lymphocytes identifiable at the clonal level, supporting the hypothesis that autoreactive peripheral T lymphocytes may mediate or participate in the pathogenesis of this disorder.     

Reconstitution of peripheral blood B cells after depletion with rituximab in patients with rheumatoid arthritis

OBJECTIVE: To study the quantitative and phenotypic reconstitution of peripheral blood B cells and its relationship to the dynamics of clinical response in patients with rheumatoid arthritis (RA) following B cell depletion with rituximab. METHODS: Twenty-four patients with active RA treated with rituximab were studied. Flow cytometry with combinations of monoclonal antibodies to B cell and T cell subsets was used. RESULTS: The frequency and total number of CD19+ cells in the peripheral blood decreased a mean of 97% for more than 3 months in all but 1 patient following rituximab therapy. All B cell populations were depleted. More than 80% of residual B cells showed a memory or plasma cell precursor phenotype. B cell repopulation occurred a mean of 8 months after treatment and was dependent on the formation of naive B cells, which showed an increased expression of CD38 and CD5. During repopulation, increased numbers of circulating immature B cells, CD19+,IgD+,CD38(high),CD10(low),CD24(high) cells, were identified. Patients who experienced a relapse of RA on return of B cells tended to show repopulation with higher numbers of memory B cells. A small number of T cells and natural killer cells expressed low levels of CD20. These cells were depleted following rituximab therapy and returned to the circulation a mean of 5 months after treatment. No other significant changes were detected in the T cell populations studied. CONCLUSION: Rituximab induced a profound depletion of all peripheral blood B cell populations in patients with RA. Repopulation occurred mainly with naive mature and immature B cells. Patients whose RA relapsed on return of B cells tended to show repopulation with higher numbers of memory B cells.     

肝炎肝硬化患者外周血Ⅱ型树突状细胞数量和功能变化及意义

目的 分析乙型肝炎病毒(HBV)引起的肝炎肝硬化患者外周血Ⅱ型树突状细胞(pDC2)的数量和产生α干扰素的功能，并分析其与患者淋巴细胞亚群和发生机会性感染的关系。方法 采用流式细胞分析技术对27例HBV引起的肝炎肝硬化患者进行研究，对患者外周血pDC2和淋巴细胞亚群进行检测；用体外灭活的Ⅰ型单纯疱疹病毒(HSV-1)刺激并培养外周血单个核细胞(PBMCs)，检测培养上清液中α干扰素的产量。结果 肝炎肝硬化患者pDC2的比例、细胞数和产生α干扰素的功能均降低；pDC2的数量与CDs^ T细胞及NK细胞数量高低存在正相关，而且发生机会性感染组患者的pDC2、CDs^ T细胞及NK细胞数均低于未感染组。结论 肝炎肝硬化患者外周血pDC2数量和功能下降，伴随CDs^ T细胞和NK细胞数平行降低，与肝炎肝硬化疾病进程和机会性感染有关。     

Immune status in Crohn's disease : 3. Peripheral blood B lymphocytes, enumerated by means of F(ab)2-antibody fragments, Null and T lymphocytes

In the peripheral blood of patients with Crohn's disease (CD) the numerical distribution of the three major B lymphocyte subsets was determined by the identification of surface immunoglobulins using F(ab)₂-antibody fragments. T cell counts were also obtained and the number of null cells was calculated. Twenty-eight patients with Crohn's disease including 14 patients with previously untreated and very short-standing disease (group CD 1) and 14 patients with long-standing and/or previous drug treated disease (group CD 2) were compared with 28 sex and age-matched normals as well as with 13 patients with acute inflammatory bowel disease (group D). Patients in group D and inactive patients of group CD 1 showed a significant absolute lymphocytosis due to an increase in both the three B cell subsets and the T cells, without changes in the null cells. While the proportion of T cells was normal, there was a significant relative B lymphocytosis and a relative null cytopenia in these patients. Active CD 1 patients, however, showed significantly lower absolute lymphocyte and T cell numbers. In group CD 2, there was a significant absolute lymphopenia caused by an equal decrease in B and T cells. Highly active CD 2 patients showed higher absolute null cell counts than inactive patients. With increasing disease duration there was a significant decrease of the relative and absolute B cell concentrations. The data obtained suggest that T and B cell populations in the peripheral blood are reduced in certain patients with Crohn's disease and that this occurs secondarily to activity of disease, chronicity of disease, and the effects of therapy.