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IgA, IgE, IgG and IgM plasma cells in small bowel mucosal biopsies from 15 controls, 16 untreated and 14 treated coeliac patients and five patients with selective serum IgA deficiency (four of whom also had coeliac disease) were quantified using an indirect immunoperoxidase technique. The IgA, IgG and IgM plasma cell counts were significantly increased in the untreated coeliac patients. The cell counts were intermediate in the treated coeliac group. These changes were in parallel to production in vitro of IgA and sIgA, IgG, and IgM by cultured mucosal biopsies from the same patients. The IgA deficient patients had very few mucosal IgA cells but elevated IgG and IgM plasma cell numbers; again these changes were reflected in the production in vitro of immunoglobulins. IgE plasma cell counts were very low in all patients and there were no differences between patient groups. The changes in cell counts and mucosal immunoglobulin production were not reflected in serum IgA, IgM and IgG concentrations but serum secretory IgA was significantly elevated in the untreated coeliac patients compared with controls, with the treated coeliac patients being intermediate. The raised mucosal plasma cell counts reflect the local mucosal production of immunoglobulin but not the immunoglobulin concentrations of serum, emphasising the importance of studying the immune function of the gut itself in coeliac disease rather than immunological abnormalities in serum.

The production of immunoglobulins by jejunal mucosa during organ culture has been studied. In 18 untreated coeliac patients the amounts of IgA, secretory IgA and IgM in the culture medium were higher than in those from 17 normal controls. The results in 15 treated coeliac patients did not differ from the control subjects. Mucosal biopsies from patients with serum IgA deficiency produced very little IgA, but large amounts of IgG and IgM. The addition of neither Frazer's gluten fraction III, nor alpha-gliadin to the culture system stimulated any additional increased secretion of immunoglobulins from the untreated coeliac patients. Production of IgA and IgM by the small bowel mucosa continues during organ culture, but that of IgG appears insignificant.

The role of gliadin antibodies in coeliac disease is unknown. We have investigated this by maintaining jejunal biopsies from control subjects, treated and untreated coeliac patients in organ culture for 24 h. The tissue culture supernatants were assayed by enzyme-linked immunosorbent assay (ELISA) for total IgG, IgM and IgA, anti-gliadin and casein antibodies. Jejunal biopsies from untreated coeliac patients secreted more total IgM and IgA but not IgG, than biopsies from control subjects: values for treated coeliac patients were similar to those from control subjects. There was increased secretion of IgG and IgM gliadin antibody, but not casein antibody, by jejunal biopsies from untreated coeliac patients compared with those from control subjects. [ABSTRACT FROM AUTHOR]