ACCUMULATION OF IMMUNOGLOBULIN-CONTAINING CELLS IN THE GUT MUCOSA ANDPRESENCE OF FECAL IMMUNOGLOBULIN IN SEVERE COMBINED IMMUNODEFICIENT (SCID) MICE WITH T-CELL-INDUCED INFLAMMATORY BOWEL-DISEASE (IBD)

mice transplanted either with a gut wall graft or with low numbers of purified CD4(+) T cells from immunocompetent syngeneic donor mice show clinical signs of IBD 3-4 months post-transplantation. The disease is mediated by mucosa-infiltrating CD4(+) TCR alpha beta(+) T cells. The pathology of 52 individual colon segments obtained from 20 gut wall- or CD4(+) T cell-transplanted diseased scid mice was evaluated by hist ology and the numbers of infiltrating immunoglobulin-containing cells were determined. In particular, cells positive for IgM, IgA and non-in flammatory immunoglobulin isotypes such as IgG1 and IgC2b were found t o accumulate in colon segments displaying the most severe histopatholo gy, including inflammatory cellular infiltration, epithelial hyperplas ia and ulcerative lesions. Compared with colon segments of normal C.B- 17 mice, the lesional scid colon shows increased levels of cells posit ive for the IgG classes. Faecal extracts of the CD4(+) T cell-transpla nted scid mice revealed the presence of all six murine immunoglobulin isotypes. Disease progression was accompanied by an increased level of excreted IgM and IgG3 and decreased levels of IgA. It is concluded th at locally secreted immunoglobulins may play an immunomodulating role in the pathological changes observed in the present model of T cell-in duced inflammatory bowel disease.