T-Cell Helper Activity and B-Cell Function of Synovial and Blood Lymphocytes from Patients with Rheumatoid Arthritis or Other Forms of Chronic Arthritis

The helper effect of T cells on B-cell immunoglobulin (Ig) responses induced by pokeweed mitogen (PWM) or purified protein derivative of tuberculin (PPD) was studied in lymphocytes from synovial fluid (SF) and blood of nine patients with rheumatoid arthritis (RA) and eight patients with other forms of chronic arthritis. In PWM cultures the helper effect of SF T cells on Ig responses (IgG, IgM, IgA) of autologous and allogeneic blood B cells was lower than that of blood T cells (P less than 0.01). This decrease was more pronounced in patients with RA than in patients with non-RA. In PPD cultures no significant difference was found between the helper effect of SF T cells and blood T cells on the Ig responses of allogeneic blood B cells or on the IgG response of autologous blood B cells, whereas the helper effect of SF T cells on the IgM and IgA responses of autologous blood B cells was decreased. The Ig responses to PWM or PPD in cocultures of autologous blood B and T cells were not significantly different between patients and healthy controls. The PWM- and PPD-induced Ig responses of SF B cells were lower than those of blood B cells when cocultured with autologous blood T cells. SF B cells produced IgG but usually little IgM and IgA. Thus there was a dysfunction of SF B cells and of SF T cells in a PWM-driven system, but a fairly good helper function of SF T cells in a PPD-driven system.     

Analysis of IgG subclass production in cell cultures from IgA deficient patients and in normal controls as a function of age

IgA deficient individuals may also have low serum levels of IgG subclasses, especially IgG2. In the present study we examined the development of plasma cells producing IgM, IgA or IgG, and the IgG1 and IgG2 subclasses, following lipopolysaccharide (LPS) and pokeweed mitogen (PWM) stimulation of mononuclear cells (MNC) from normal and IgA deficient individuals as a function of age. Studies of blood MNC from 38 normal donors (age range 2-44 years) revealed an age-related distribution pattern of mu, gamma, alpha, gamma 1 and gamma 2 plasma cells produced in mitogen-stimulated and control cultures. Decreased IgA responses to both LPS and PWM were consistently observed in cultures of MNC from all of the nine children with IgA deficiency. When compared with age-matched controls the IgG response was also diminished in PWM stimulated cultures, whereas the IgM responses were normal. The IgG deficit was due to reduced responses for the gamma 1 and gamma 2 subclasses, and was most pronounced for IgG2; IgG2 plasma cell differentiation was particularly depressed in LPS cultures. In contrast to normal adult cells, blood MNC from the nine children with IgA deficiency and age-matched controls (2-17 years) yielded more IgG1 than IgG2 plasma cells in both control and LPS cultures, while the pattern of response to PWM was similar in all groups (gamma 1 greater than gamma 2). A good concordance was found between the level of secreted Ig in the culture supernatants and the relative number of IgM or, IgG and IgA plasma cells identified by immunofluorescence staining of cytoplasmic immunoglobulins.     

Circulating and pokeweed mitogen-induced immunoglobulin-secreting cells in systemic lupus erythematosus.

Peripheral blood mononuclear cells (PBM) obtained from patients with active untreated systemic lupus erythematosus (SLE) were evaluated both for the number of cells spontaneously secreting immunoglobulin (Ig) as well as for their capacity to generate immunoglobulin-secreting cells (ISC) in vitro in response to pokeweed mitogen (PWM). ISC were enumerated by a reverse haemolytic plaque assay designed to quantify the number of cells secreting IgG, IgM and IgA. PBM obtained from eight patients with active untreated SLE contained markedly increased numbers of ISC compared to age-, sex-, and race-matched normal control PBM. SLE PBM contained a mean of 13,805 +/- 3266 ISC per 10(6) cells, of which 74% secreted IgG, 10% IgM and 22% IgA, while normal PBM contained a mean of 779 +/- 143 ISC per 10(6) cells, with 57% secreting IgG, 25% IgM and 33% IgA. PBM obtained from SLE patients were also examined for their ability to generate ISC in vitro in response to PWM. SLE PBM were markedly deficient in their capacity to respond to PWM with the differentiation of ISC. This diminished responsiveness could not be ascribed to serum factors, the presence of increased numbers of cells with suppressive capacity or the absence of potentially responsive B cells. Rather, a deficiency of helper T cell activity appeared to be responsible. This was indicated by the observation that PWM responsiveness could be restored to SLE PBM by co-culturing them with purified mitomycin C-treated normal T cells.     

Evidence for a malignant proliferation of IgE-class specific helper T cells in a patient with Sézary syndrome exhibiting massive hyperimmunoglobulinemia E

Peripheral blood mononuclear cells (PBM) from a patient with Sézary syndrome exhibiting massive hyperimmunoglobulinemia E were examined in vitro. The patient's PBM and B cells (Bp) but not normal individuals' PBM and B cells (Bn) produced spontaneously large amounts of IgE. The addition of pokeweed mitogen (PWM) did not affect IgE production by both the patient's and normal individuals' PBM. The IgE production by PWM-stimulated Bp was depressed when cocultured with normal T cells but not depressed with the patient's T cells (Tp). When Tp were cocultured with Bn, significantly larger than expected quantities of IgE were produced. Ig assay of the same supernates showed that Tp had significantly less helper activities for IgG, IgA, and IgM production. Almost all Tp possessed the Leu3a and Leu3b antigens which are expressed on the helper/inducer T cell subset. These results indicate that the neoplastic cells in this patient originated from a subset of T cells programmed not for IgG, IgA, and IgM, but for IgE synthesis.     

Aberrant immunoregulatory control of B lymphocyte function in lepromatous leprosy.

The capacity of peripheral blood mononuclear (PBM) cells from patients with leprosy to generate immunoglobulin-secreting cells in response to pokeweed mitogen (PWM) was evaluated by a reverse haemolytic plaque forming cell (PFC) assay. The PFC responses of PBM cells from patients with lepromatous (Lpr) leprosy were significantly higher (P less than 0.01) than those of PBM cells from normal controls and patients with tuberculoid leprosy. Co-culture of T lymphocytes from normal donors with PBM cells from Lpr patients reduced the PFC response of these cells to the normal range. T4+-helper lymphocytes from Lpr donors did not induce supranormal responses to PWM by normal PBM cells enriched for B lymphocytes. T8+-suppressor lymphocytes from normal donors greatly reduced the response of cultures containing normal allogeneic B cells plus T4+ cells. Conversely, when T8+ cells from Lpr donors were cocultured with normal B cells plus T4+ cells, they failed to suppress the response to PWM. In summary, these studies have demonstrated abnormally high PWM-stimulated PFC responses by B lymphocytes from patients with Lpr leprosy. This aberration, in turn, is associated with a loss of regulatory function by T8+-suppressor cells in Lpr patients.     

In vitro synthesis of IgE by human lymphocytes. I. The spontaneous secretion of IgE by B lymphocytes from allergic individuals: a model to investigate the regulation of human IgE synthesis

In view of the controversial data in the literature regarding the in vitro IgE synthesis by human lymphocytes, the conditions for culture of lymphocytes and the methodology for measurement of the IgE produced are described in detail. In the absence of any added mitogen, enriched B cell preparations derived from 70% of allergic donors actively secreted 100 to 3200 pg/ml of IgE after culture for 7 days, at which time the cell viability was higher than 85%. In comparable B cell cultures derived from non-allergic donors, only trace amounts of de novo synthesized IgE were detected in 20% of the cases. All B cell cultures actively secreted IgG, IgA, IgM and there was no apparent relationship between the secretion of IgE and that of the other classes of Ig. By contrast, the synthesis of IgE by unfractionated peripheral blood mononuclear cells of allergic individuals, which were stimulated with pokeweed mitogen (PWM) under several experimental conditions, was not consistently reproducible, i.e. the spontaneous synthesis of IgE in such cultures was either suppressed or enhanced by PWM. The most important finding was that the secretion of IgE was selectively enhanced by supplementing the B cell cultures with cell-free supernatants (CFS) of cultures of neonatal lymphocytes which had been preincubated with 10 micrograms/ml IgE. It is, therefore, concluded that B cell cultures from allergic individuals constitute an appropriate model for investigations of the mechanisms underlying the regulation of human IgE synthesis.     

Synergistic effects of human B and T lymphocyte mitogens induce uniform,high levels of immunoglobulin secretion among normal donors

Synergistic effects of B-cell mitogen Staphylococcus bacteria strain Cowan I (Cowan I) plus T-cell activator pokeweed mitogen (PWM) in generating immunoglobulin-secreting cells (ISC) from human peripheral blood mononuclear cells (MNC) were investigated. ISC were assayed by reverse plaque-forming cells using protein A-coated red blood cells. Low concentrations of PWM plus Cowan I gave superadditive effects on ISI induction, generating 3–20 times as many ISC as optimal amounts of either mitogen alone. The mitogens together and separately showed similar kinetics of ISC; synergy was observed at every day tested. IgM ISC represented 10% of initial MNC from all cell donors tested even if the donors were low responders to either mitogen alone. The numbers of ISC obtained are higher than previous reports and more uniform among donors, making this a superlative method for studies on normal human immunoglobulin secretion.     

T cell dependent differentiation of human B cells: direct switch from IgM to IgE, and sequential switch from IgM via IgG to IgA production.

Ig production by splenic human B cells that express different surface Ig isotypes were analysed in limiting dilution cultures. Therefore, FACS sorted IgM+, IgG+ and IgA1+ B cells were stimulated with PMA-activated EL4 thymoma cells as helper cells in the presence of IL-2 and IL-4. We found that at least every second B cell responded in vitro and secreted the antibody corresponding to its surface Ig isotype. IgE secreting cells developed from surface IgM+ D+ cells (1/31 to 1/167), but not from IgG+ or IgA1+ cells (much less than 1/5000). Negative signalling of the IgM+ B cells by addition of anti-IgM antibodies into the cultures reduced the number of single IgM producing cells by greater than 85%, and completely inhibited IgE switch. In contrast, anti-IgG and anti-IgA antibodies did not reduce the IgE response. The results indicate a direct switch from IgM to IgE secretion in vitro. In contrast to IgE, IgA secreting cells developed from IgM+D+ (1/30 to 1/51) and from IgG+ B cells (1/14 to 1/25). Negative signalling of the IgG+ B cell subset within total B cells by anti-IgG antibodies suppressed the development of IgG as well as IgA producing cells, but did not inhibit IgM and IgE responses. This indicates a sequential switch from IgM via IgG to IgA. Taken together, this study indicates that IgE secreting cells are derived directly from IgM+D+ B cells by non-sequential switching, whereas IgA producing cells preferentially develop by sequential switching via IgG+ B cells.     

Immunosuppression caused by antigen feeding II. Suppressor T cells mask Peyer's patch B cell priming to orally administered antigen

Peyer's patch (PP) cells transferred into sublethally irradiated recipients generated substantial IgM, IgG and IgA anti-sheep red blood cell (SRBC) plaque-forming cell (PFC) responses in the recipient spleen. If donor mice were given SRBC orally for 4–5 weeks prior to transfer, the adoptively transferred PP IgG and IgA responses were considerably suppressed, although the IgM responses were often unaffected. Co-injection of PP cells from antigen-fed mice with PP cells from normal mice resulted in marked suppression of the normal PP IgG and IgA response. However, treatment of PP cells from antigen-fed mice with anti-Thy-1.2 plus complement prior to cotransfer completely abrogated suppression of the IgG PFC response and partially abrogated the suppressed IgA response. B cells from the PP of antigen-fed mice, when transferred into SRBC-primed irradiated recipients (to provide T cell help) generated 2–3 times more IgG and IgA PFC than comparable numbers of B cells from the PP of normal mice. Thus antigen feeding generates suppressor T cells in PP which can mask the expression of B cell priming to orally administered antigen.     

Defective neutrophil and lymphocyte function in leucocyte adhesion deficiency.

We report a Chinese girl with the moderate phenotype of leucocyte adhesion deficiency (LAD), presenting with persistent omphalitis and recurrent soft tissue infections. She had subnormal adhesion-dependent neutrophil functions, such as chemotaxis and chemiluminescence response to a particulate stimulant (opsonised zymosan). Despite her adequate humoral response to documented herpes simplex virus type 1, parainfluenza type 2 and adenovirus infection in vivo, there was marked impairment in the generation of plaque-forming cells (PFC) driven by pokeweed mitogen (PWM) in vitro. IgM PFC were less severely affected than IgG and IgA PFC, probably because IgM production is less dependent on T cell help than IgA and IgG production. The patient's B cells and accessory cells had reduced function compared with the control subsets, while helper function of her CD4+ cells was virtually absent in the PWM-driven PFC assay. She also had marked defect in natural killer cell activity. The proliferation of her lymphocytes was normal to several plant lectins, including phytohaemagglutinin, concanavalin A and PWM, but markedly defective to OKT3.     

IgM- and IgD-bearing peripheral blood lymphocytes differentiate to IgM but not IgG or IgA immunoglobulin-secreting cells

Human peripheral blood mononuclear cells were depleted of surface IgM⁺ or IgD⁺ cells and assayed for mitogen-induced differentiation to immunoglobulin-secreting cells (ISC) of IgM, IgG and IgA classes. Stimulatory agents included T cell-dependent poke weed mitogen, B cell mitogen Staphylococcus aureus bacteria strain Cowan I, and a combination of the two which gives uniform, high levels of ISC from all normal donors. Depletion of either IgM- or IgD-bearing B lymphocytes resulted in loss of cells bearing the other Ig class and blocked most of the mitogenic reactivity to anti-IgM and anti-IgD. Proliferative responses to Cowan I in these depleted populations were about 20% that of unfractionated mononuclear cells. Depletion of T cells increased the mitogenic response to Cowan I and to the two antibody preparations, showing that they are T-independent mitogens. Depletion of IgD⁺ cells caused partial loss of mitogen-induced IgM ISC (22%-60% of unseparated controls) but no loss of IgG or IgA ISC. Depletion of IgM-bearing cells caused complete loss of IgM ISC, but no loss of IgG or IgA ISC. We previously demonstrated that anti-IgM antibody blocked mitogen induction of Ig secretion of these three classes in spleen cells, but only IgM secretion in blood mononuclear cells. Together, the results suggest that the majority of cells in normal blood responding to mitogens to mature to IgG or IgA production belong to IgM^?, IgD^? B cell subsets, in contrast to precursors of secreting cells for these isotypes in the spleen. Thus, these blood precursors appear to be more mature than the corresponding spleen cells.     

Delineation of producing ability of IgG and IgA subclasses by naive B cells in newborn infants and adult individuals

Neonatal B cells with the naive (sIgD⁺) phenotype are able to generate IgG- and IgA-producing cells as well as IgM production in the presence of memory CD4⁺ T cells expressing L-selectin (CD62L) in pokeweed mitogen-stimulated cultures. We used this system to examine comparatively the ability of naive B cells to produce IgG and IgA subclasses in newborn infants and adult individuals. Naive B cells were enriched from both donors on the basis of sIgD positivity, and memory (CD45RO⁺) CD4⁺ T cells with CD62L expression were isolated from adults. We here demonstrate some differences in profiles of IgG and IgA subclass production between neonatal and adult naive B cells. In neonatal B cells, IgG1 and IgG3 were predominantly produced, but IgG2 and IgG4 production was virtually absent. Similar to neonatal B cells, adult naive B cells produced mainly IgGq and IgG3, although memory (sIgD’) B cells from adults secreted all of the IgG subclasses. It should be noted that low but detectable levels of IgG2 and IgG4 were found in adults’naive B cell cultures. Although IgA produced by neonatal B cells was exclusively IgA1, IgA2-secreting cells were identifiable in adult naive B cells. The results suggest that further class switch of naive B cells to IgG2, IgG4 and IgA2 in addition to IgG1 and IgG3 may be controlled by their own age-dependent maturation process.     

Con A-propagated, auto-reactive T cell clones that secrete factors promoting high IgA responses

Four BALB/c T cell clones from among a set propagated in the presence of concanavalin A (Con A) were selected on the basis of their ability to produce supernatant factors promoting high IgA plaque-forming cell (PFC) responses by 2,4,6-trinitrophenyl-conjugated keyhole limpet hemocyanin (TNP-KLH)-primed splenic B cells in the presence of TNP-SRBC. Such clones could be derived from cultures containing T cells not only from gut-associated lymphoid tissue, but also from the spleen. The selected clones all proliferated well in the presence of syngeneic, irradiated APC without either Con A or exogenous IL-2, but required both APC and Con A to produce helper factors. Factors from three of the clones helped B cells both to proliferate and to differentiate into IgM, IgG and IgA PFC. Factors from the fourth clone helped B cells differentiate into IgA and IgG PFC and may have promoted switching to these isotypes but did not support either B cell proliferation or generation of IgM PFC. Cross-linking of B cell receptors for antigen was not required for the response to the helper factors since TNP-SRBC were unnecessary and high concentrations of them were actually inhibitory.     

Human tonsillar IgE biosynthesis in vitro. I. Enhancement of IgE and IgG synthesis in the presence of pokeweed mitogen by T-cell irradiation

A study of the events regulating human IgE biosynthesis in vitro was undertaken with tonsillar lymphocytes. IgG synthesis was also studied to evaluate the specificity of our observations. T-cell irradiation significantly enhanced synthesis of IgE by pokeweed mitogen (PWM)-stimulated B cells from 12 of 18 donors and IgG in all 18 donors. This enhancement was the result of de novo immunoglobulin synthesis, since the amount of IgE and IgG spontaneously released from lysed and lysed-and-cultured mononuclear cells was significantly less than that detected in the cell cultures, and the augmentation was completely ablated by the treatment of the cells with cycloheximide or mitomycin C. Enhancement was also dependent on the presence of PWM; T-cell irradiation did not enhance IgE synthesis in unstimulated cultures. Moreover, this enhancement was also observed in the co-cultures of B cells and allogeneic irradiated T cells. These observations suggest that radiosensitive T cells exert a suppressive activity that contributes to regulation of human IgE and IgG synthesis and that the suppressor function as well as the helper function can overcome allogeneic disparities.     

Enhancement of IgE synthesis and histamine release by T cell factors derived from atopic patients with bronchial asthma

Culture supernatants of unstimulated T cells (TCS) derived from normal donors or from atopic patients with bronchial asthma were tested for their ability to regulate the spontaneous IgE synthesis by B cells of normal and atopic subjects. The same TCS were also tested for their influence on the histamine release from leukocytes of house dust mites-sensitive patients. Addition of TCS to B cell cultures from allergic donors induced a dose-dependent increase of the spontaneous IgE production without affecting the synthesis of IgG, IgM, and IgA. The potentiating activity of TCS was observed only in B cell cultures spontaneously producing IgE; TCS were still active on irradiated B cells. The maximal IgE-enhancing activity was observed when TCS were added at the onset of B cell cultures. The supernatants of T cells lysed at day 0 did not contain IgE-potentiating factors. The antigen-induced but not the spontaneous histamine release from leukocytes of house dust mite-sensitive patients was enhanced by pretreatment with TCS from allergic donors. The enhancing activities of TCS on IgE synthesis and on histamine release could be removed by absorption with IgE-Sepharose and subsequently recovered by elution with glycine buffer. The results indicate that T cells of patients with asthma spontaneously release IgE-binding factors capable of increasing both the spontaneous IgE synthesis by B cells and the antigen-induced histamine release.     

Human tonsillar IgE biosynthesis in vitro. II. Analysis of T cell regulation with monoclonal antibodies

Phenotypes of T cells regulating human tonsillar IgE biosynthesis in vitro were studied by use of Leu 2a and Leu 3a monoclonal antibodies that recognize T cell subsets. B cells cultured with Leu 3a+-enriched populations (B cells plus T3a) produced significantly more IgE and IgG in the presence of pokeweed mitogen than B cells with the Leu 2a+-enriched populations (B cells plus T2a) (p less than 0.001 for IgE and p less than 0.001 for IgG). No significant differences were observed in IgE and IgG synthesis between the cultures of B cells alone and B cells plus T2a. T2a, but not T3a cells, significantly suppressed IgE synthesis (p less than 0.05 for geometric means and p less than 0.001 for percent suppression) when the cells were added to cultures of B cells plus T3a. Suppression of IgG synthesis was not observed under conditions that suppressed IgE synthesis, suggesting qualitative and quantitative differences in regulation of production of these isotypes. When T2a cells were irradiated, the suppressor activity disappeared. When graded numbers of T3a cells were added to B cells, it was noted that IgE synthesis first increased and then decreased as the numbers of T3a were increased. When the T3a cells were irradiated, IgE biosynthesis was suppressed at lower T/B ratios (less than 1 in four of five experiments) and was enhanced at higher T/B ratios (greater than 1 in all five experiments). Similar results were observed in experiments with OKT4 and OKT8 monoclonal antibodies. It is concluded that phenotypes of helper T cells for IgE synthesis are Leu 3a+ or OKT4+ and that IgE suppressors are predominantly Leu 2a+ or OKT8+ and are radiosensitive, as reported for regulation of other isotypes. However, it is suggested that Leu 3a+ and OKT4+ cells consist of radioresistant and radiosensitive helper cells and, presumably, a minor population of suppressor cells.     

Distribution of Ig Classes and IgG Subclasses among Human B Cells Activated by Nocardia opaca-Delipidated Cell Mitogen or by Pokeweed Mitogen

The relative proportions of cells synthesizing the three major Ig classes or one of the four IgG subclasses in cultures stimulated with pokeweed mitogen (PWM) or Nocardia-delipidated cell mitogen (NDCM) were investigated. In cultures of human peripheral blood mononuclear cells (PB MNC) stimulated with PWM, the number of IgG-containing cells (CC) was higher than the number of IgM-CC, and a substantial number of IgA-CC was found. Conversely, in NDCM-stimulated PB MNC cultures IgM-CC outnumbered IgG-CC and only few IgA-CC were detected. In those cultures, the removal of T cells resulted in an increase in the number of IgM-CC concomitant with a decrease in the number of IgG-CC. A substantial number of cells containing simultaneously IgG or IgA in addition to IgM could be found in PWM-stimulated cultures. These cells were virtually absent in NDCM-stimulated cultures. The relative proportions of IgG subclass-CC were IgG1-CC greater than IgG2-CC greater than IgG3-CC greater than or equal to IgG4-CC in PWM-stimulated and IgG2-CC greater than IgG1-CC greater than IgG3-CC greater than or equal to IgG4-CC in NDCM-stimulated cultures. The removal of T cells from NDCM-stimulated cultures did not result in major alteration of this distribution. The role of T cells and of the genomic order of the Igh-C genes in their phenotypic expression triggered in vitro by PBA is discussed.     

Dendritic cells support production of IgA and other non-IgM isotypes in clonal microculture

Microcultures of helper T (Th) cells and a few appropriately primed murine B cells can be used to detect cognate T-B interactions which lead to clonal production of IgM, IgG1, and IgE. However, IgG2, IgG3, and IgA are very rarely expressed. We have found that the addition of dendritic cells to such cultures creates an extremely supportive environment for clones expressing IgA with other isotypes, as well as clones expressing only detectable IgA. Typically, 400 dendritic cells were added to 3000 conalbumin-specific Th cells (D10.G4.1) and 30 hapten-specific Peyer's patch (PP) B cells with antigen in 15 microliters. The response was antigen dependent and clonal. Almost half of the clones expressed only non-IgM isotypes, 43% expressed some IgA, and 14% expressed some IgG3; isotype diversity increased over time. Dendritic cells from PP and spleen were found to be equally supportive, and allowed the number of T cells required in microculture to be decreased from 3000 to 400. However, T cell proliferation was not required for the supportive effect of dendritic cells. Surface IgD-bearing cells were also found to switch to IgA production in microculture as judged by their generating clones expressing IgM along with IgA and other isotypes. Again, IgA was usually expressed only in the presence of dendritic cells. The mechanism may involve dendritic cell-induced T cell activation and/or dendritic cell factors, and is under investigation.     

Functional assessment of a B cell defect in patients with selective IgA deficiency

The cellular basis of selective IgA deficiency was investigated by examining the terminal differentiation of B lymphocytes co-cultured with varying ratios of T lymphocytes in the presence of pokeweed mitogen. Eight patients were studied who had serum IgA concentrations <0·05 mg/ml, salivary IgA <0·01 mg/ml, and between 0·8 and 4% lymphocytes with surface IgA markers. Peripheral blood lymphocytes from patients and normal donors were separated into B cell (non T cell) and T cell fractions by E-rosetting. Microcultures were established at eleven B cell to T cell ratios from 100% B cells to 100% T cells. After 7 days, immunoglobulin in the supernatant fluid was measured by radioimmunoassay. Cultures containing patients' B cells and either autologous or allogeneic T cells produced very low or undetectable amounts of IgA. However, cultures from six out of eight patients contained cells with intracytoplasmic IgA. Secretion of IgM by the patients' B cells was identical to that of normal donors. Surprisingly, IgG production by patients' B cells was less than that produced by normal B cells especially in the mid-range ratios of the microcultures. Production of IgA, IgG and IgM by normal B cells from peripheral blood or tonsils was very similar in the presence of normal T cells or patients' T cells. In cultures containing optimal ratios of normal B cells, the patients' T cells not only did not suppress IgA production but also gave normal help for IgA production. It was concluded, on the basis of these studies, that a defect in patients with selective IgA deficiency was the functional inability of their B cells to produce normal amounts of IgA in vitro even when provided with normal allogeneic T cell help.     

Interleukin-4 suppresses immunoglobulin production by peripheral blood lymphocytes of patients with common variable immunodeficiency (CVI) induced by supernatants of T cell clones.

Supernatants of both CD4+ and CD8+ alloreactive T cell clones induced IgM, IgG and IgA synthesis by peripheral blood lymphocytes (PBL) of healthy donors in vitro. These supernatants were also tested on their capacity to induce immunoglobulin production by PBL of four patients with CVI and one patient with CVI and thymoma. A low degree of IgM, IgG and IgA production was induced in one patient with CVI. In the patient with CVI and thymoma, induction of IgG and IgA synthesis was in the normal range, whereas IgM production was reduced. In the three other patients only a low production of IgM was induced. Interestingly, pre-incubation of the PBL for 24 h with interleukin-4 (IL-4) suppressed immunoglobulin production both by PBL of the patients with CVI and healthy donors. The strongest inhibitory effects were observed on IgA synthesis. These data indicate that B cells of three patients with CVI can not be induced to switch to IgG or IgA producing cells in vitro. In contrast, B cells of the patient with CVI and thymoma were able to respond to the relevant B cell growth and differentiation factors present in the T cell clone supernatants, suggesting that the T cells of this patient may fail to produce these factors. However, the proliferative responses of the T cells to phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM), were normal in all five patients tested. In addition, the interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production by PBL of the five patients was also in the normal range. Although only a small number of patients was tested, these results support the view that defects in both regulatory T cell functions and/or intrinsic B cell defects may contribute to the pathogenesis of CVI.