Polyclonal immunoglobulin secretion in patients with common variable immunodeficiency using monoclonal B cell differentiation factors

Impaired up-regulation of CD70 and CD86 in naive (CD27-) B cells from patients with common variable immunodeficiency (CVID)

CVID is characterized by reduced serum levels of all switched immunoglobulin isotypes (IgG, IgA, IgE) predisposing patients to recurrent infections of their respiratory and gastrointestinal tract. Correspondingly, most CVID patients exhibit a severely decreased proportion of class switched memory B cells (CD19+CD27+IgD-IgM-IgG+ or IgA+) in their peripheral blood (CVID type I). We previously identified a subgroup of CVID patients showing a significantly reduced expression of CD86 and CD137 following activation in vitro of PBMC or purified B cells (CD19+) with anti-IgM plus IL-2. Here we extend our previous studies by asking whether highly purified, cell-sorted naive B cells show already an expression defect of B cell surface molecules relevant in activation (CD39, CD69), differentiation (CD24, CD27, CD38) or T-B interaction (CD25, CD70, CD86). We stimulated cell-sorted, naive B cells (CD19+CD27-IgM+IgDhighIgG-IgA-) from 10 CVID patients and 10 healthy controls for 4 days with anti-IgM plus IL-2 in the absence or presence of autologous CD4+ T cells and measured the expression of the referred surface molecules. Based on reduced or normal numbers of switched memory B cells the CVID patients had previously been classified into eight type I patients and two type II patients, respectively. Interestingly, only the molecules CD25, CD70 and CD86, all relevant in cognate T-B interaction, showed a significantly lower expression in naive B cells from CVID patients compared to controls. While coculture with autologous CD4+ T cells normalized the CD25 expression, CD70 and CD86 expression remained subnormal, notably in the eight CVID patients of type I. These findings strongly suggest an intrinsic signalling or expression defect for CD70/CD86 at the level of naive B cells in type I CVID patients.

CD40:CD40L interactions in X-linked and non-X-linked hyper-IgM syndromes

Hyper-IgM (HIM) syndrome is a rare immunodeficiency characterized by low or absent IgG, IgA, and IgE with normal or elevated levels of IgM. This disorder can be acquired or familial with either X-linked or autosomal patterns of inheritance. The X-linked form of the disease is a consequence of mutations in the CD40 ligand (CD40L) gene that encodes a protein expressed primarily on activated CD4+ T cells. The cognate interaction between CD40L on T cells and CD40 on antigen-stimulated B cells, macrophage, and dendritic cells is critical for the development of a comprehensive immune response. The non-X-linked form of HIM syndrome is heterogeneous and appears in some cases to be a consequence of mutations in the AlD gene which encodes a B cell specific protein required for class switch recombination, somatic mutation, and germinal center formation. However, mutations in other unidentified genes are clearly the basis of the disease in a subset of patients. In this article, we review the essential features of the X-linked and non-X-linked forms of HIM syndrome and discuss the critical role the CD40:CD40L receptor-ligand pair plays in the pathogenesis of these immune deficiencies.

Defective surface expression of attractin on T cells in patients with common variable immunodeficiency (CVID)

The proliferative responses of T lymphocytes of a subset of patients with CVID are abnormally low. This may be due to abnormalities in extracellular interactions or signalling defects downstream from membrane-associated receptors. Demonstrating that the T cell receptor signalling was normal, we observed no abnormal pattern of activation-induced tyrosine phosphorylation in cells from CVID patients. Moreover, the addition of exogenous IL-2 increased the low proliferation to mitogens, thus indicating the integrity of the IL-2R signalling apparatus. Attractin is a rapidly expressed T cell activation antigen involved in forming an association between T cells and monocytes. Twenty-four to 48 h after activation by CD3 cross-linking, attractin expression was not up-regulated on the cells of CVID patients despite normal up-regulation of CD25 and CD26. On control cells, however, attractin expression was up-regulated together with CD25 and CD26. The addition of the purified 175-kD attractin was capable of restoring the proliferative response of peripheral blood mononuclear cells following CD3 X-L in the presence of suboptimal concentrations of rIL-2 (10 and 20 U/ml). The effect was dose-dependent with the maximal effect at a concentration of 500 ng/ml, and present at a concentration as low as 50 ng/ml. Due to the likely role of attractin in cell guidance and amplification of the immune response, our results indicate that the lack of up-regulation of the molecule in patients with CVID may in turn affect any further step of productive immune response. Our finding may also imply a potential therapeutic role for this novel molecule.

Increased Activation of Protein Kinase A Type I Contributes to the T Cell Deficiency in Common Variable Immunodeficiency

The molecular mechanisms underlying the T cell dysfunction often present in common variable immunodeficiency (CVI) are not established. cAMP-dependent protein kinase A type I (PKAI) is an important inhibitor of T cell proliferation after Ag stimulation. We therefore investigated the possibility that activation of PKAI may be involved in the development of T cell dysfunction in CVI. An exogenously added PKAI-selective antagonist (Rp-8-Br-cAMPS) induced a significant increase in anti-CD3-stimulated PBMC proliferation in 20 CVI patients compared with no effect in 15 controls. Purified T cells from 7 CVI patients with strictly defined T cell deficiency had elevated endogenous cAMP levels compared with controls. Treatment of T cells from these CVI patients with Rp-8-bromo-cAMP-phosphorothioate markedly improved anti-CD3-stimulated proliferation (up to 3.7-fold), particularly in CD4+ lymphocytes, reaching proliferation levels comparable to control values. No effect of cAMP antagonist on T cell proliferation was seen in controls. In these CVI patients, cAMP antagonist also increased IL-2 production in anti-CD3-stimulated T cells. However, exogenously added IL-2 at concentrations comparable to the achieved increase in IL-2 levels after addition of cAMP antagonist had no effect on T cell proliferation. Furthermore, the stimulatory effects of exogenously added IL-2 at higher concentrations and cAMP antagonist on T cell proliferation were additive. Our findings indicate that increased PKAI activation may be an important molecular basis for the T cell defect in CVI and suggest that the cAMP/PKAI system may be a potential molecular target for immunomodulating therapy in these patients.

The Regulation and Functional Consequence of Proinflammatory Cytokine Binding on Human Intestinal Epithelial Cells

Products of an activated immune system may affect cells within the immune system as well as nonlymphoid cells in the local environment. Given the immunologically activated state of the intestinal tract, it is conceivable that locally produced cytokines could regulate epithelial cell function. To assess whether epithelial cells are targets for particular cytokines, we initiated studies on the binding of a panel of proinflammatory cytokines in freshly isolated epithelial cells from normal and inflammatory bowel disease (IBD) patients as well as in cell lines. Isolated intestinal epithelial cells (IEC) were stained with phycoerythrin-conjugated or biotinylated cytokines to determine the expression and density of receptors for IL-1β, IL-6, granulocyte-macrophage CSF (GM-CSF), and TNF-α. Receptors for IL-1β, IL-6, and GM-CSF were readily detectable in all epithelial cell preparations at levels equal to (GM-CSFR) or lower than those seen on monocytes. However TNFα-R were not detectable on freshly isolated IECs. Receptor density was greater in surface vs crypt epithelial cells, but no significant differences were seen between normal and IBD epithelial cells. Expression of IL-1R and IL-6R was enhanced by LPS and IFN-γ. Functionally, IL-1β enhanced proliferation of the IEC cell line, DLD1, whereas GM-CSF treatment of de-differentiated crypt-like DLD1 and HT29 cells resulted in enhanced expression of ICAM-1. Furthermore, TNF-α treatment enhanced the secretion of IL-8 and GRO-α in HT29 cells, but not in freshly isolated IEC cultures. The differential binding and function of proinflammatory cytokines on IEC support the hypothesis that these cytokines may be involved in normal physiological processes as well as in regulating mucosal immune responses.

IL-10 production in common variable immunodeficiency

Common variable immunodeficiency, (CVI) is a heterogeneous primary immunodeficiency disease in which there are T and B cell defects. Since IL-10 in conjunction with anti-CD40 promotes secretion of IgG, IgA, and IgM by CVI B cells, these studies were performed to investigate IL-10 production in CVI. Mitogen or anti-CD3 stimulated CVI peripheral blood mononuclear cells, or isolated T cells produced an insignificant amount of IL-10 over background levels. CVI monocyte IL-10 production was substantial and greater than that of normal controls. Anti-IL-10-neutralizing antibody strongly enhanced CVI T cell proliferative responses to PHA, but only to an insignificant extent, soluble antigens. IL-2 plus anti-IL-10 enhanced CVI proliferative responses to antigens significantly more over baseline than for cells of similarly tested normal controls. These data suggest that CVI T cell secretion of IL-10 is deficient, but that monocyte-derived IL-10, plus a relative lack of IL-2 production, could contribute to the defects of cell proliferation in this disorder.

Immunologic effects of low-dose polyethylene glycol-conjugated recombinant human interleukin-2 in common variable immunodeficiency

Children or adults with the primary immunodeficiency disease, common variable immunodeficiency (CVI), have abnormally low levels of at least two of the three serum Ig isotypes. Although there appear to be intrinsic B cell defects, many have poor T cell proliferation and deficient secretion of IL-2, IL-4, IL-5 interferon-gamma, and B cell differentiation factor. Because the addition of various T cell factors can enhance Ig secretion in vitro in CVI, we have hypothesized that the B cells in this disease may be defective because they lack appropriate investigating the in vivo effects of recombinant IL-2 using a new biologic, polyethylene glycol-conjugated recombinant IL-2 (PEG-IL-2). In these studies, CVI patients were treated with weekly subcutaneous injections of PEG-IL-2. After 12 weeks, each patient had enhanced T cell proliferation, normal IL-2 production, boosted BCDF secretion, and B cells responsive to differentiation signals. During PEG-IL-2 treatment, four of five patients produced detectable serum antibody to keyhole limpet hemocyanin. These data suggest that CVI, which has the phenotype of B cell deficiency, may be caused by a lack of appropriate T cell signals for B cell maturation.

Defective CD2 T cell pathway activation in common variable immunodeficiency (CVID)

Clonal T cell expansion requires simultaneous activation of the TCR and secondary signals, e.g. CD2, CD4, CD28. Interference of CD2/CD58 interaction with MoAbs abrogates the primary immune response and antibody production. Given this functional importance of CD2/CD58 interaction for the generation of specific immune responses, we demonstrate for the first time a defective CD2 pathway activation in patients with CVID (seven children and four adults). The costimulatory effect of monocytes upon CD2-triggered proliferation was significantly impaired in CVID patients: 4.080 ct/min versus 20.769 ct/min in controls (P < 0.05). Second, IL-1, which is a strong comitogenic factor for activation via CD2 in normal T cells, showed a defective amplifier function of the CD2 pathway in most patients (median 1.714 ct/min in patients versus 17.521 ct/min in controls; P < 0.05). In addition, by using a mitogenic combination of CD2 plus CD45 MoAb, median proliferation of T cells was severely depressed in patients: 10.577 ct/min versus 34.685 ct/min in controls (P = 0.005). In conclusion, the marked dysfunction seen in responsiveness to phytohaemagglutinin (PHA) (median 24.594 ct/min in patients versus 52.229 ct/min in controls; P < 0.001) and after CD2 triggering, together with the unaffected response to TCR-CD3, suggest that the T cell deficiency in CVID is in part due to deficiencies in the CD2 pathway. Since direct activation of protein kinase C(PKC) by phorbol ester restores defective T cell responses to normal, our results suggest that an early signal-transducing defect might exist at a step proximal to PKC activation in patients with CVID.

CD40 ligand expression is defective in a subset of patients with common variable immunodeficiency

Common variable immunodeficiency (CVI) is characterized by hypogammaglobulinemia and recurrent bacterial infections due to failure of CVI B cells to differentiate in vivo into immunoglobulin-secreting plasma cells. We hypothesized that T-cell dysfunction resulting in abnormal contact-mediated B-cell activation may play a prominent role in the failure of CVI B cells to produce specific antibody. We have previously shown that B-cell proliferation and IgE production after stimulation with anti-CD40 and interleukin (IL) 4 were normal in 22 CVI patients evaluated, indicating that CVI B cells respond to signals delivered via CD40. Here we report that CD40 ligand (gp39) mRNA expression by activated lymphocytes from CVI patients (n = 31) as a group was significantly depressed (P < 0.0001) compared with normal controls (n = 32). gp39 mRNA expression by activated lymphocytes from 13 CVI patients fell below the normal control range. T-cell surface expression of functional gp39 protein was correspondingly low in those patients with gp39 mRNA levels below normal control range and normal in patients with gp39 mRNA levels within normal control range. In CVI patients as a group, gp39 mRNA levels correlated with IL-2 mRNA levels (P < 0.002, r = 0.6) and production (P < 0.001, r = 0.7) but not with gene expression or production of other lymphokines evaluated, suggesting an as-yet-undetermined association between gp39 and IL-2 gene regulation. Of the 13 patients whose activated T cells exhibited gp39 mRNA expression below the normal control range, 2 had normal T-cell-derived lymphokine production, whereas the remaining 11 exhibited broader T-cell dysfunction, resulting in IL-2 deficiency, and in some patients deficient production of other lymphokines as well, reflecting a heterogeneity in the underlying mechanisms leading to depressed gp39 expression in these patients. The observation that both gene and surface expression of gp39 by activated T cells is depressed in a subgroup of CVI patients suggests that inefficient signaling via CD40 may be responsible, in part, for failure of B-cell differentiation in these patients.

Activated B cells from patients with common variable immunodeficiency proliferate and synthesize immunoglobulin

Most patients with common variable immunodeficiency (CVI) have normal numbers of circulating B cells but low concentrations of serum Ig. To determine if the hypogammaglobulinemia is caused by an intrinsic B cell defect, we studied B cell function of 22 CVI patients. Cultured B cells from all CVI patients underwent normal proliferation and synthesized normal quantities of IgE in the presence of anti-CD40 and IL-4. If cultured with anti-CD40 and IL-10, four patterns of Ig isotype synthesis were observed. Six CVI patients produced normal amounts of IgM, IgG, and IgA. Four patients produced normal quantities of IgM and IgG. Of the remaining 12 patients who failed to synthesize IgG and IgA, 8 produced normal and 4 synthesized decreased amounts of IgM. Analysis of the IgG subclasses produced by 10 patients with IgG-secreting B cells revealed that IgG4 was the most affected subclass, followed by IgG2; synthesis of IgG3 and IgG1 remained normal. Similarly, in the six IgA producing patients, IgA2 was more often affected than IgA1. The hierarchy of Ig isotype and subclass synthesis corresponds to Ig heavy chain constant region gene location on chromosome 14. Thus, circulating B cells of CVI patients are committed to synthesize one or more Ig isotypes or subclasses, and under proper conditions can proliferate, mature into Ig-secreting cells, and undergo class switch to IgE.

Reduced interleukin-2 (IL-2) production in common variable immunodeficiency is due to a primary abnormality of CD4+ T cell differentiation

Common variable immunodeficiency (CVI) is a condition characterized by hypogammaglobulinemia and impaired antibody responses, resulting in recurrent bacterial infections in untreated patients. In addition, affected individuals exhibit an increased incidence of autoimmunity, malignancy, and certain viral infections, suggesting the presence of an underlying generalized immune dysregulation. We have previously described a subgroup of CVI patients in whom T cells within PBMC populations exhibit a selective defect in lymphokine production. IL-2, IL-4, and IL-5 mRNA production was impaired in these patients, while proliferation, IL-2R expression, and c-myc mRNA production were normal. In the present series of experiments, using highly purified CD4+ T cells prepared by negative selection, we show that this lymphokine production defect is a primary abnormality of CVI CD4+ T cells: whereas CD4+ T cells from CVI patients proliferate normally in response to stimulation by PHA, staphylococcal enterotoxin B (SEB), or anti-CD2 antibodies, these stimuli induce significantly less IL-2 production than observed with CD4+ T cells from normal individuals. Furthermore, we show that this IL-2 production defect is not due to an accessory cell abnormality, since it was seen in the presence of normal (allogeneic) accessory cells, and patient accessory cells supported normal amounts of IL-2 production by PHA-stimulated CD4+ T cells obtained from normal individuals. Of interest, we also found that while IL-2 production by CD4+ T cells from CVI patients induced by stimulation with immobilized anti-CD3 antibody was reduced compared to CD4+ T cells from normal control individuals, this reduction was not statistically significant. Furthermore, stimulation of both CVI patient and normal CD4+ T cells with either ionomycin+phorbol myristate acetate or a combination of immobilized anti-CD3 antibody plus anti-CD28 antibody resulted in a 50-fold increase in IL-2 production compared to stimulation with immobilized anti-CD3 antibody alone, and, under these conditions, CVI and normal CD4+ T cells produced equivalent amounts of IL-2. Finally, minor defects in interferon-gamma production by CD4+ T cells from CVI donors were observed, but these were less severe than the IL-2 production defects and were not statistically significant. We conclude that a primary abnormality of lymphokine production exists in the CD4+ T cells of a subset of patients with CVI.(ABSTRACT TRUNCATED AT 400 WORDS)

Increased IL-6 gene expression and production in patients with common variable immunodeficiency

We have studied IL-6 gene expression and production by in vitro stimulated peripheral blood mononuclear cells (PBMC) isolated from common variable immunodeficiency (CVI) patients. A strong hybridization signal for the IL-6 probe was observed in mRNA extracted from phytohaemagglutinin (PHA)- and PHA/phorbol myristate acetate (PMA)-stimulated PBMC from most of 12 CVI patients analysed. IL-6 production by PHA-stimulated PBMC from 28 CVI patients was evaluated in ELISA and found to be significantly (P < 0.0001) higher than in normal controls. IL-6 production, however, did not correlate with the lymphocyte populations examined, nor with the absolute number of monocytes. We have also showed that IL-6 was able to increase IgM secretion by several Epstein-Barr virus (EBV)-transformed cell lines derived from both normal donors and CVI patients, but it failed to modify substantially the amounts of IgM and IgG produced in vitro by PBMC derived from CVI patients and activated with pokeweed mitogen (PWM) or anti-IgM. Our data indicate that IL-6 gene expression and production is increased in CVI, but CVI cells do not respond to IL-6 with increased production of immunoglobulin.

B cells from subjects with CVI can be driven to Ig production in response to CD40 stimulation

The majority of patients with common variable immunodeficiency (CVI) have low to normal numbers of membrane Ig-bearing B cells; yet these cells fail to differentiate in vivo resulting in hypogammaglobulinemia. We have suggested that the differentiation failure of CVI B cells is related to a failure to respond appropriately to signals involved in terminal B cell differentiation as most CVI subjects' cells undergo activation and proliferation normally. Whether this failure relates to a direct "intrinsic" defect in the B cells or is secondary to a lack of appropriate T cell or other influences in vivo is uncertain. We have previously reported that the majority of patients with CVI have elevated circulating levels of IL-6. We now show that the IL-6 produced by these patients is functionally normal. Additionally, the display of IL-6 receptors on in vitro stimulated CVI B cells is normal. However, we found that the patients' cells do not make IgE in response to an IL-6/T-cell-dependent differentiation pathway employing exogenous interleukin-4 (IL-4). The failure to respond in the IL-6-dependent system could not be overcome by exogenous IL-6 or varying doses of IL-4. In contrast, when stimulated by CD40 plus IL-4 in a differentiation pathway that does not require IL-6, B cells from CVI patients were stimulated to produce IgE. These findings, along with our earlier data showing that 13-cis-retinoic acid can drive maturation in CVI patients, strengthen the concept that B cells in patients with CVI have the potential for terminal differentiation but do not appear to achieve this in vitro or in vivo through a polyclonal Ig differentiation pathway that employs IL-6 as one of its maturation signals.

Restoration of immunoglobulin secretion in vitro in common variable immunodeficiency by in vivo treatment with polyethylene glycol-conjugated human recombinant interleukin-2

Patients with common variable immunodeficiency (CVI) have decreased immunoglobulin levels resulting in frequent infections. Although previous studies have suggested that the B cell is intrinsically defective, numerous T cell deficiencies, including reduced interleukin-2 (IL-2) production, have been described. Since the addition of T cell cytokines to CVI B cells can increase Ig secretion in vitro, hypogammaglobulinemia in CVI may be due to defective T cell functions. To assess this possibility directly, we treated five CVI patients intravenously with a new biologic, human recombinant IL-2 conjugated to polyethylene glycol. Doses were 250,000 IU/m2 weekly for Weeks 1-4, 500,000 IU/m2 for Weeks 5-8, and 10(6) IU/m2 for Weeks 9-12. During and after treatment, B cells of all patients secreted 10- to 1000-fold more Ig in vitro. There was also a striking improvement in T cell helper activity since T cells of treated patients could induce 10- to 10,000-fold increases in Ig secretion by B cells from normal donors. No increase was seen in serum Igs during the study, but the anti-tetanus antibody of the IgG isotype could be detected in cell culture supernatants. Whether the effects of infused polyethylene glycol IL-2 are mediated through T or B cells, or both, is still unknown. However, these data reinforce the concept that CVI B cells may be competent, but, lacking essential T cell growth factors, in vivo maturation to Ig production does not occur.

Cytokines regulating human B cell growth and differentiation

Utilizing a model system of anti-CD3-stimulated T cells, we have identified a potent B cell differentiation factor (BCDF) in the supernatant of these cells. This factor, 446-BCDF, appears to act on SAC-activated B cells inducing a 10- to 100-fold increase in Ig secretion. 446-BCDF has an apparent MW of 32 kDa and a pI of 6.0. Its activity cannot be inhibited by an anti-IL-6 antiserum, and activity is enhanced after passage over an anti-IL-6 affinity column. 446-BCDF activity is detected in the 50 mM salt fraction eluted from a Mono Q column. This 50 mM fraction has the only activity detected after passage over an anti-IL-6 affinity column and migrates with an apparent pI of 6.0. Taken together these data suggest that 446-BCDF is a unique potent polyclonal human BCDF which may be a predominant factor regulating terminal B cell differentiation.

Abnormalities in CD4+ T lymphocyte subsets in patients with common variable immunodeficiency

In order to investigate whether deficient immunoglobulin production in common variable immunodeficiency (CVI) patients was related to defective T cells functions, phenotype and proliferative responses to mitogen of peripheral blood mononuclear cells (PBMC) were investigated in 9 patients with CVI. The results were compared to those of 12 age- and sex-matched normal controls. The numbers of CD3+ and CD8+ T cells in the patients were not different from those in the control group, but the numbers of CD4 T cells were decreased (511 +/- 237 vs 844 +/- 247/mm3; P less than 0.01). The decrease in CD4 T cells was due to a dramatic deficiency in the CD4+ CD45RA+ subset, observed as an absolute value of blood lymphocytes (126 +/- 91 vs 384 +/- 142; P less than 0.001) and as a percentage (9.0 +/- 7.1 vs 18.8 +/- 5.0; P less than 0.01). In contrast, the CD4+ CD29+ T cell subset was not different in CVI from those in the control group. Moreover, there was a strong positive correlation between the number of percentages of CD4+ CD45RA+ blood T cells and the proliferative response of PBMC to PHA (respectively, P less than or equal to 0.02 and P = 0.05) and to Con A (P less than or equal to 0.02). The decrease of CD4+ CD45RA+ T cells could reflect an abnormality in the physiological status of T cells and could be of critical importance in the antibody deficiency.

Abnormal response to a human B cell growth factor in patients with common variable immunodeficiency (CVI)

Patients with common variable immunodeficiency (CVI) generally fail to produce antigen-specific IgG. We have identified a lymphokine called high molecular weight B cell growth factor (HMW BCGF) that expands an IgG-producing subpopulation of B cells. The B cells from 15 of 16 patients with CVI evaluated in this study failed to proliferate to HMW BCGF, although they proliferated normally to another BCGF, low molecular weight BCGF (LMW BCGF). Nevertheless, 11 patients had more than normal numbers of B cells expressing HMW BCGF receptors. The HMW BCGF receptors on the B cells of three patients with CVI studied were the same molecular weight as the normal HMW BCGF receptor. Examination of B cells from four patients with CVI for intracellular signals produced in normal B cells after stimulation with HMW BCGF revealed that B cells from patients with CVI failed to developed significant increases in cyclic adenosine monophosphate or phosphoinositides after HMW BCGF stimulation. However, cytoplasmic phosphoinositides in the B cells from all four patients with CVI were already increased above what is observed in normal B cells before stimulation with HMW BCGF (either freshly isolated or Staphylococcus aureus Cowan I-activated B cell). Thus, the failure of B cells from patients with CVI to respond to HMW BCGF may be related to their abnormal activation in vivo. Since HMW BCGF expands a subpopulation of memory B cells, the inability of CVI B cells to respond to HMW BCGF may contribute to their abnormal secondary responses to antigens.

Evidence for accessory cell function by class II MHC antigen-expressing airway epithelial cells

Expression of major histocompatibility complex (MHC) class II antigens is a requirement for accessory cell function in antigen presentation. Recent reports have demonstrated the presence of class II antigens on human bronchial epithelial cells. In the present study, immunohistochemical staining revealed HLA-DR on human airway epithelial cells obtained from two different mucosal sites (lobar bronchus and nasal turbinates). To determine whether airway epithelial cells bear functional class II molecules that allow for their cognate interaction with T lymphocytes, cells isolated from these sites were used in mixed lymphocyte cultures (MLR), as an in vitro model of accessory cell function. Freshly isolated cells (11 bronchi/3 turbinates) stimulated allogeneic T lymphocytes (stimulation index [S.I.] = 9.3 [mean]; P less than 0.001 compared to T cells alone). In order to assess the potential role of contaminating conventional accessory cells, bronchial epithelial cell isolates were first preincubated in a serum-free, growth factor-supplemented medium that functionally eliminates potential non-epithelial stimulators prior to MLR culture. Conventional accessory cell-depleted epithelial cells were still capable of stimulating allogenic T lymphocytes in 18 of 23 MLR cultures (S.I. = 5.5 [mean]; P less than 0.0005 compared to T cells alone). The addition of an anti-class II monoclonal antibody (VG2.2) at the onset of culture completely inhibited the MLR response (n = 10). No shift in the CD4+/CD8+ ratio was detected between lymphocytes harvested from airway epithelial cell MLR (1.42 +/- 1.29) and the ratio from T lymphocytes cultured alone (1.3 +/- 0.75), suggesting that both CD4+ and CD8+ T lymphocytes were proliferating in response to stimulation from alloepitopes recognized on airway epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Limited B cell repertoire in severe combined immunodeficient mice engrafted with peripheral blood mononuclear cells derived from immunodeficient or normal humans

The ability to engraft human PBMC or fetal tissue immune cells in the severe combined immunodeficient (SCID) mouse has created a need for characterization of these systems and their application to disease models. We demonstrate that SCID mice reconstituted with PBMC support the growth and differentiation of a restricted set of B cells. Human IgG levels of 1-2 mg/ml (10-20% of normal human serum levels) were routinely achieved in spite of a serum half life of only 12 d. Ig levels peaked around 50 d and Ig production was maintained for greater than 100 d. The Ig was greater than 85% IgG though some IgM, IgA, IgD, and even IgE could be detected. However, the human IgG produced in hu-PBL-SCID mice was pauci-clonal when analyzed by isoelectric focusing and by kappa/lambda light chain usage. Using a new polymerase chain reaction based analysis capable of monitoring individual VH family utilization, we found that the engrafted B cells showed skewed and restricted human VH subfamily utilization. These parameters were markedly variable among hu-PBL-SCID mice reconstituted from the same donor cell population at both early (21-50 d) and late stages (greater than 100 d). Hu-PBL/CVI-SCID mice constructed with cells from patients with common variable immunodeficiency with an in vitro block in terminal B cell differentiation produced human Ig responses that were quantitatively the same as those produced by hu-PBL-SCID mice from normal donors. The hu-PBL-SCID system using PBMC appears to lead to growth and Ig production by a small number of B cells and results in a restricted B cell repertoire.

Lack of induction of suppressor T cells by intestinal epithelial cells from patients with inflammatory bowel disease

The mechanisms underlying the chronic unrelenting inflammatory response seen in inflammatory bowel disease (IBD) are poorly understood. We have recently proposed a novel role for the normal intestinal enterocyte, that of antigen presenting cell. However, in contrast to conventional antigen presenting cells, normal enterocytes appear to selectively activate CD8+ antigen nonspecific suppressor T cells. To determine whether failure of this process may be occurring in inflammatory bowel disease, freshly isolated enterocytes from small and large bowel from normal patients, patients with Crohn's disease, ulcerative colitis, and inflammatory (diverticulitis, ischemic colitis, and gold induced colitis) controls were co-cultured with allogeneic T cells in a modified mixed lymphocyte reaction. In contrast to normal enterocytes, 42/42 Crohn's and 35/38 ulcerative colitis-derived epithelial cells stimulated CD4+ T cells, whereas 65/66 and 9/9 normal and inflammatory control enterocytes, respectively, stimulated CD8+ T cells (as previously described), suggesting that the results seen were not just a reflection of underlying inflammation. Furthermore, IBD enterocytes from both histologically involved and uninvolved tissue were similar in their ability to selectively activate CD4+ T cells, speaking for a more global defect in epithelial cells in IBD. Finally, activated T cells from IBD epithelial cell-stimulated mixed lymphocyte cultures displayed potent T helper activity in an antigen nonspecific fashion. Taken together, these data suggest that there may be an intrinsic defect in epithelial cells from patients with IBD, resulting in the inability to normally stimulate suppressor T cells in an antigen overloaded environment.

The capacity of interleukin-4 to induce in vitro IgE synthesis by B cells of patients with common variable immunodeficiency

Interleukin-4 (IL-4) has been shown to induce IgE synthesis by peripheral blood mononuclear cells (PBMC) of normal donors in vitro. However, induction of PBMC of patients with common variable immunodeficiency (CVI) with IL-4 resulted in IgE production in only two out of eight cases tested. PBMC of the first patient that produced IgE in response to IL-4 also secreted normal levels of IL-4 upon activation. PBMC of the second patient secreted very low levels of IL-4 in vitro which may account for the very low serum IgE levels in this patient. Of the other six patients who had very low serum IgE levels and whose PBMC failed to produce IgE in response to IL-4 in vitro, five did not secrete IL-4 upon in vitro activation. The capacity of the T cells to produce IL-4 was intact in the sixth patient. Collectively our data indicate that PBMC of the majority of patients with CVI are defective since they failed to respond appropriately to IL-4 and they failed to produce IL-4, contributing to the view that CVI is a heterogeneous disorder in which a variety of T and B cell defects occur.

Classification of patients with common variable immunodeficiency by B cell secretion of IgM and IgG in response to anti-IgM and interleukin-2

We have classified patients with common variable immunodeficiency (CVI) on the basis of the ability of their B cells to respond to anti-IgM and interleukin (IL)-2 in vitro. Group A had cells unable to secrete IgM or IgG, Group B secreted IgM alone, and Group C secreted both IgM and IgG. A separate small group of patients lacked peripheral B cells. Where Ig secretion was present with anti-IgM and IL-2, EBV increased it, but where it was absent, EBV only induced IgM secretion in two out of eight Group A patients and IgG in one out of five Group B patients. These classifications are related to the sex of the patient and may represent different loci of the block in B-cell differentiation in CVI.

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.

Peripheral blood lymphocytes of patients with common variable immunodeficiency (CVI) produce reduced levels of interleukin-4, interleukin-2 and interferon-gamma, but proliferate normally upon activation by mitogens

Peripheral blood lymphocytes (PBL) of 11 patients with CVI produced reduced levels of interleukin-4 (IL-4) upon activation by mitogens as compared with those secreted by PBL of healthy donors. The interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production by PBL of a series of 15 patients with CVI was also reduced. Decreased levels of IL-4 or IL-2 and IFN-gamma production were not only observed after activation by phytohaemagglutinin (PHA) at concentrations of 10 and 1 micrograms/ml, but also after activation by concanavalin A (Con A, 10 micrograms/ml). Longitudinal studies indicated that this defective lymphokine production was consistent upon testing periods up to 5 months. No correlation between reduced IL-4, IL-2 or IFN-gamma production was observed. PBL of patients that produced reduced levels of one lymphokine generally secreted normal levels of the other two lymphokines. Despite the reduced synthesis of the T cell growth factors IL-2 and IL-4, the proliferative responses of the PBL of the patients were in the normal range, which is compatible with the finding that IL-2 and IL-4 have synergistic effects on lymphocyte proliferation, particularly when one of these lymphokines is present at suboptimal concentrations. Since IL-2, IL-4 and IFN-gamma can act as B cell growth and differentiation factors, our data suggest that the reduced synthesis of these lymphokines may contribute to the deficient immunoglobulin production in patients with CVI.

Regulation of interleukin 6 receptor expression in human monocytes and monocyte-derived macrophages. Comparison with the expression in human hepatocytes

IL-6 is a cytokine with pleiotropic biological functions, including induction of the hepatic acute phase response and differentiation of activated B cells into Ig-secreting plasma cells. We found that human peripheral blood monocytes express the IL-6-R, which is undetectable on the large majority of lymphocytes of healthy individuals. Stimulation of monocytes by endotoxin or IL-1 causes a rapid downregulation of IL-6-R mRNA levels and a concomitant enhancement of IL-6 mRNA expression. IL-6 itself was found to suppress the IL-6-R at high concentrations. A gradual decrease of IL-6-R mRNA levels was observed along in vitro maturation of monocytes into macrophages. We show that downregulation of IL-6-R mRNA levels by IL-1 and IL-6 is monocyte specific, since IL-6-R expression is stimulated by both IL-1 and IL-6 in cultured human primary hepatocytes. Our data indicate that under noninflammatory conditions, monocytes may play a role in binding of trace amounts of circulating IL-6. Repression of monocytic IL-6-R and stimulation of hepatocytic IL-6-R synthesis may represent a shift of the IL-6 tissue targets under inflammatory conditions.

The role of lymphokines in common variable hypogammaglobulinemia

Common variable (acquired) hypogammaglobulinemia (CVH) is a rare primary immunodeficiency disease of great interest as an immunological model of defects in antibody production. In this article, Gavin Spickett and John Farrant discuss evidence of abnormalities in lymphokine production and responses in the generation of the functional failure. It is not yet clear whether the B cell is intrinsically abnormal or lacks appropriate signals, but the block appears to occur in the differentiation phase of B cells, since membrane (but not secreted) IgG is made. Some T-cell defects also occur in this disease. The cause of CVH is unknown, although a viral aetiology has been suggested. Better understanding of lymphokine networks may allow the provision of specific signals to overcome the block in antibody production.

Clinical and immunologic analyses of 103 patients with common variable immunodeficiency

Common variable immunodeficiency (CVI) or hypogammaglobulinemia is a heterogeneous primary immunodeficiency disease in which B cells produce little or no antibody. Since the disease is relatively rare and the spectrum of associated illnesses is broad, patients are given care by a variety of specialists. Thus it has been difficult to determine the incidence of specific complications. In these studies we analyzed 103 consecutively referred CVI patients of age range 3-71 years (average, 29 years) who were followed for a period of 1-13 years (total of 750 patient years). The average serum IgG was 174.4 mg/dl for untreated patients and 301 mg/dl for patients treated with intramuscular immunoglobulin at the time of the first visit. The average IgA was 14.5, and the average IgM was 80.7, with no difference between or after immunoglobulin treatment. About one-half of the patients had T-cell dysfunction, but lymphocyte stimulation responses were inversely related to age, which implies worsened T-cell immunity with age. Serum IgG and IgA levels were found to be statistically associated (P = 0.008), and serum IgG was related to lymphocyte stimulation with concanavalin A (P = 0.01). By 1986, 79 patients were alive, 23 had died, and 1 could not be located. Recurrent bacterial illnesses were common to all patients, and 22% had developed chronic lung disease, 22% autoimmune disease, 15% cancer, 13% hepatitis, and 9% malabsorption. Autoimmune disease was more common in females, and cancer was more likely to develop in the fifth and sixth decades. In 11% of the group, other family members were found to be immunodeficient (hypogammaglobulinemic or IgA deficient). Nine patients died of respiratory insufficiency (with or without other complications), and seven patients died of cancer. These data provide valuable information about the immunologic abnormalities and the spectrum and frequency of illnesses associated with hypogammaglobulinemia.

In vitro induction of T cell-dependent B cell differentiation in patients with common varied immunodeficiency

Patients with common varied immunodeficiency (CVI) are characterized by hypogammaglobulinemia. We investigated in vitro T cell-dependent B cell differentiation in CVI peripheral blood mononuclear cells by stimulating the T cells with an anti-CD3 (T3) monoclonal antibody. In cultures from CVI patients with no detectable circulating B cells, little immunoglobulin (Ig) was produced following anti-CD3 stimulation. In cultures from CVI patients with near-normal numbers of circulating B cells, anti-CD3 stimulation induced a normal percentage increase in Ig-secreting cells and appreciable (albeit subnormal) increases in IgG and IgM secretion. Cell-mixing experiments pointed to a quantitative, rather than qualitative, defect in B cell function in most of these CVI patients. Nevertheless, CVI T cells can induce substantial differentiation of autologous (and normal) B cells following anti-CD3 stimulation (which may mimic physiologic stimulation). This raises the possibility of correcting the hypogammaglobulinemia of CVI by in vivo or ex vivo administration of appropriate T cell stimuli.

Inhibition of T cell-dependent human B cell proliferation and B cell differentiation by polyspecific monomeric IgG

A commercially available polyspecific, monomeric IgG preparation suitable for intravenous administration (IgSRK; Sandoglobulin) can inhibit pokeweed mitogen (PWM)-induced proliferation of peripheral blood mononuclear cells (PBMC) by a small, but statistically significant, amount compared to control cultures. Such inhibition could not be demonstrated when PBMC were stimulated with the T cell mitogen phytohaemagglutinin. Surface phenotype analysis of the PWM-stimulated cells indicated that in IgSRK-containing cultures, the proportion of B cells was decreased and the proportion of T cells was increased compared to control cultures. This alteration in T:B ratio was not due to antigenic modulation of B or T cell markers from their surfaces. In addition, IgSRK inhibited the proliferation of T cell-depleted PBMC cultures stimulated by B cell proliferation factors (BCPF) but not by fixed protein A-bearing Staphylococcus aureus strain Cowan I. The capacity to inhibit B cell proliferation was independent of and distinct from its capacity to inhibit B cell differentiation, since IgSRK inhibited the differentiation of a B cell differentiation factor (BCDF)-sensitive line by BCDF (which contains no BCPF activity). IgSRK inhibited PWM-induced generation of cytoplasmic Ig+ cells but had no effect on Ig secretion from mature Ig-secreting cells. Taken together, these findings suggest that IgSRK (which contains the IgG fraction from pooled plasma from 2,000 healthy donors) can inhibit T cell-dependent or T cell factor-dependent B cell proliferation and B cell differentiation.

Evidence for function of Ia molecules on gut epithelial cells in man

Using freshly isolated Ia+ gut epithelial cells we have been able to demonstrate that these cells can function as accessory cells in an immune response. The cells can act as stimulators in both autologous and allogeneic MLRs. More importantly, these cells are capable of taking up the soluble antigen, tetanus toxoid, processing it, and presenting it to tetanus-primed T cells. These functions appear to relate to the presence of surface Ia in that a hetero-anti-Ia antibody can block these effects. Noteworthy is the finding that the subpopulation of T cells stimulated when epithelial cells are used as accessory cells is the T8+, 9.3-T cell. These cells function as potent antigen-nonspecific suppressor cells in both MLR, T cell antigen responses, and induction of B cell differentiation by PWM. These findings have significant implications in local gut immune responses and may help explain several poorly characterized phenomena of mucosal immunity.

Terminal maturation of resting B cells by proliferation-independent B cells differentiation factors

Using response to four different BCDF preparations as a model of B cell maturation, we have shown that induction of B cell proliferation abrogates terminal maturation of these cells. In fact, response to some BCDFs can occur in the presence of inhibitors of DNA replication, suggesting that there are proliferation-independent as well as proliferation-dependent BCDFs. These findings cannot be explained by changes in the kinetics of the BCDF response, nor can they be reversed by repletion of media or changing cell densities. Proliferation-independent BCDFs appear to exert their effects on dense, resting 4F2- B cells rather than more activated B cells. This is in contrast to B cell differentiation signals of IL-2 alone or SAC and IL-2 in concert. These data suggest that the current models of B cell activation and maturation may require some reorganization, relegating the proliferative phase of B cell maturation to a lesser role. In addition, evidence is provided for the fact that the resting B cell may have the full complement of receptors for BCDF as well as BCGF and BCPF and may help account for the inherent nonspecificity of the immune response.

Pulmonary sarcoidosis associated with acquired humoral and cellular immunodeficiency

A previously healthy 27-year-old man with class II pulmonary sarcoidosis developed severe humoral immunodeficiency within the course of the disease with an IgG of less than 250 mg/ml and undetectable levels of IgA and IgM. Repeated skin tests were negative for seven common recall antigens. Cellular blood test demonstrated normal numbers of B cells and slight T-cell lymphopenia with a normal T-helper/suppressor subset distribution (ratio 1.6). In contrast, parallel examination of the bronchial alveolar lavage fluid (BAL) demonstrated highly elevated numbers of T cells with a subset ratio of 3.1 and significant numbers of activated T cells as revealed by the expression of Ia and Tac antigens. Functional in vitro assays showed a greatly decreased mitogenic response of blood T cells and diminished production of immunoglobulins. These data indicate that, despite a severely depressed systemic humoral and cellular immune system, T-cell activation can take place at the inflammatory site, potentially causing the lesions characteristic of sarcoidosis.