Defective lymphocyte IgA production in inflammatory bowel disease

Evidence for non-neutralizing autoantibodies against IL-10 signalling components in patients with inflammatory bowel disease

Background

Inflammatory bowel disease constitutes a heterogeneous group of conditions, whose aetiology is only partly understood. The prevailing hypothesis on its pathogenesis is that IBD is the result of an inadequate immune response to the resident bacterial flora of the intestine. An autoimmune background, however, has been discussed since the 1950s. Lately, it has been shown that failures in interleukin-10 (IL-10) signalling due to IL-10- and IL-10 receptor (IL-10R) mutations result in IBD. Our study aimed at investigating the existence of inhibitory autoantibodies against IL-10 and IL-10R in IBD patients capable of down-modulating IL-10 signalling thereby mimicking IL-10 or IL-10R deficiency.

Results

Thirteen IBD patients had IgG autoantibodies against IL-10, IL-10RA and/or IL-10RB, and three patients had IgA autoantibodies against IL-10. However, the absolute OD values of the serum antibodies measured by ELISA were low, there was overall no significant difference between patients and controls, and positive sera had no neutralizing activity.

Conclusion

No evidence for an involvement of autoantibodies against IL-10 or IL-10R in the pathogenesis of inflammatory bowel disease could be established.

Inflammatory bowel diseases in patients with adaptive and complement immunodeficiency disorders

Crohn's disease and ulcerative colitis are idiopathic chronic inflammatory diseases that primarily affect the gastrointestinal tract. The underlying causes remain poorly understood, but there is a growing body of evidence advocating a likely primary pathogenic role for immunodeficiency in the development of Crohn's lesions. Concordantly, a number of congenital immunodeficiencies disrupting the cellular innate immune system strongly predispose to noninfectious, Crohn's-like inflammatory bowel disease. There are case reports and series suggesting that the same may be true for some of the congenital adaptive and complement immunodeficiencies. This review considers and critiques these potential associations.

A limiting-dilution analysis of activated circulating B cells in Crohn's disease

In the present study the spontaneous in vitro production of immunoglobulins G, A, and M by peripheral mononuclear cells was evaluated, in patients with Crohn's disease, in relation to the state of B-cell activation and further characterized by limiting-dilution analysis. A total of 25 patients with Crohn's disease and 10 healthy controls was studied. The proportion of the transferrin receptor-bearing cells in the B7+ subset was higher in active Crohn's disease patients than in either those with quiescent disease or controls. There was a significant rise in the in vitro IgG, IgM, and IgA production in patients with untreated active Crohn's disease compared to either those with untreated quiescent disease or controls. When patients were followed up from the active phase to clinical remission, a significant decrease in the production of IgG and IgM was observed. IgA levels also showed a decrease, although not reaching statistical significance. When the Ig production was analyzed by limiting dilution, no difference was observed between patients and controls in terms of either precursor frequency of Ig-producing cells or patterns of frequency distribution. In both patients and controls a biphasic limiting-dilution profile was observed. This study shows that a significant B-cell activation is present in Crohn's disease patients, which is accompanied by an increase in immunoglobulin production. This study also indicates that in Crohn's disease the increased immunoglobulin production is related to an augmented B-cell clone size rather than to an increased precursor frequency.

Immune functions in inflammatory bowel and coeliac diseases

Different immune functions of 10 patients with glutein-sensitive enteropathy (GSE), 9 with Crohn's disease (CD), 11 with ulcerative colitis (UC) and 13 healthy controls were characterized. The numbers of suppressor T cells in GSE were comparable to those of the controls; otherwise, the lymphocyte subpopulations were decreased in these bowel diseases. In the whole-blood cultures, the lymphocyte proliferative responses to PHA were normal in the bowel diseases, but the responses to Con A were decreased in CD. In cultures with D-penicillamine, the inhibition of the helper effect of CD patients was more pronounced in PHA-stimulated cultures than in Con A-stimulated cultures. The total Ig and IgA production did not markedly differ among the groups. PWM-induced IgM secretion was significantly decreased in GSE, CD and UC, and IgG secretion in CD and UC, as compared to controls. In GSE, an increased Con A inducible suppressor cell activity was observed in the IgM production. Altogether, no clear-cut immunological imbalance was detected in any of the bowel diseases; this in agreement with previous works. However, there are some differences in the regulatory cell balance among the patients with GSE, CD and UC. The determination of lymphocyte proliferative responses to PHA and Con A together with D-penicillamine seems to provide a new immunological criterium for distinguishing between Chrohn's disease and ulcerative colitis.

Disordered regulation of the in vitro immunoglobulin synthesis by intestinal mononuclear cells in Crohn's disease

In vitro immunoglobulin synthesis by isolated intestinal mononuclear cells of macroscopically normal mucosa from patients with Crohn's disease has been studied and results compared with those obtained with cells from normal mucosa of resection specimens from patients with colonic carcinoma, or other intestinal disorders. The total lamina propria mononuclear cells (LPMC) in Crohn's disease produced spontaneously less IgA and more IgG than the control groups, but no difference was observed for IgM. An enriched lymphocyte fraction (LPL) of the Crohn's disease patients showed a higher spontaneous synthesis of IgA and IgG when compared with controls. In contrast, another fraction enriched for macrophages (LPM) produced spontaneously less IgA, IgG, and IgM in Crohn's, than in control patients. Incubation with pokeweed mitogen (PWM) decreased immunoglobulin synthesis by LPMC in Crohn's disease and controls, and this was enhanced by simultaneous incubation with concanavalin A. In controls PWM stimulation increased immunoglobulin synthesis by LPL and decreased immunoglobulin synthesis by LPM. In Crohn's disease, however, PWM had no effect on either fraction. This study shows major differences in the regulation of the immunoglobulin synthesis by intestinal cells between Crohn's disease and controls.

Transient IgA and IgM deficiencies are frequent in children with ulcerative colitis

Serum immunoglobulin levels in 22 children with ulcerative colitis were followed for 2 years after diagnosis of the disease. A statistically significant depression of IgA, IgM, and IgG was noticed; depression of IgA and IgM was most frequent. The depression of immunoglobulin levels was transient and was most prominent during the first year of treatment. All patients in the study received sulphasalazine. Disease activity or steroid medication had no influence on immunoglobulin levels. The development of immunoglobulin deficiencies was not connected with any HLA antigen; we found decreased frequency of antigen B7 in the whole group.

Altered patterns of secretion of monomeric IgA and IgA subclass 1 by intestinal mononuclear cells in inflammatory bowel disease

Intestinal mononuclear cells (MNC) from patients with inflammatory bowel disease (IBD) demonstrated altered patterns of spontaneous secretion of immunoglobulin A (IgA). Control intestinal MNC had markedly high spontaneous secretion of IgA compared to IBD intestinal MNC. Control intestinal MNC secreted predominantly dimeric IgA (only 31% monomeric IgA), whereas IBD intestinal MNC secreted increased amounts (43%-53%) of monomeric IgA. Control intestinal MNC secreted 61% IgA subclass 1 (IgA1), whereas IBD intestinal MNC secreted 71%-74% IgA1. Intestinal MNC from involved portions of resected specimens secreted more of both monomeric IgA and IgA1 than MNC from uninvolved areas of the same bowel. Therefore, intestinal MNC from involved IBD intestinal specimens secrete less total IgA but high percentages of monomeric IgA and IgA1 compared to control intestinal MNC. This could be caused by increased homing of monomeric IgA- and IgA1-producing cells into involved intestine, or the in situ proliferation of monomeric IgA and IgA1 precursor cells resulting from immunoregulatory alterations. These observations may represent the normal mucosal IgA immune response to infectious agents or inducing factors of either a primary or a secondary nature.

Abnormalities of B-cell activation and immunoregulation in patients with Crohn's disease

We have studied B-lymphocyte function in 39 patients with Crohn's disease and 35 normal individuals using a reverse haemolytic plaque assay as the effector system. Ten patients had active Crohn's disease, the others being in an inactive state of the disease. Compared with normal individuals, the Crohn's disease patients - especially those in the active state of the disease - had markedly raised numbers of spontaneous immunoglobulin secreting cells and severely decreased responses to the polyclonal activator pokeweed mitogen. The differences between the reactivity of patients with active disease and those with inactive disease were statistically significant. These findings indicate an in vivo polyclonal B-cell activation in Crohn's disease patients, possibly due to antigen(s) or infectious agent(s). In vitro experiments were performed with separated lymphocytes in order to characterise the mechanism responsible for the altered immune reactivity in Crohn's disease. These revealed an intrinsic B-cell defect as well as an impaired T-helper cell capacity in patients with Crohn's disease. Findings supporting the hypothesis of an increased suppressor activity in Crohn's disease patients could not be observed, and marker analyses revealed normal proportions with the exception of raised Leu 7 positive cells that mediate 'natural killer' and 'killer' cytolysis. We conclude that immune dysfunction in peripheral blood lymphocytes of Crohn's disease patients involves B-cells as well as T-helper cells.

Correlation of histopathologic evidence of disease activity with the presence of immunoglobulin-containing cells in the colons of patients with inflammatory bowel disease

Immunofluorescence of formalin-fixed, paraffin-embedded tissues was performed to study the plasma cell population in 114 colonic specimens from 58 patients. Correlation of the histopathologic stage of disease activity with the isotypes and numbers of immunoglobulin-containing cells in the lamina propria demonstrated highly significant (P less than 0.001) increases in the mean numbers of IgG- (18-fold), IgA- (twofold) and IgM- (sixfold) containing cells in specimens from patients with active inflammatory bowel disease as compared with control specimens. Increased numbers of immunoglobulin-containing cells were uncommon in inactive inflammatory bowel disease and in reactive mucosa. No deposition of immunoglobulin-containing immune complexes was found at any stage of disease activity. These findings suggest that immune complex-mediated damage does not play a major role in the epithelial damage in inflammatory bowel disease. In future studies, it will be of importance to determine whether the antibody from immunoglobulin-containing cells seen in patients with inflammatory bowel disease can effect damage via an antibody-dependent cell-mediated cytotoxicity mechanism.