ABERRANT COLONIC EXPRESSION OF MHC CLASS II ANTIGENS IN HIRSCHSPRUNG'S DISEASE

The major histocompatibility complex (MHC) Class I and II cell surface antigens responsible for the recognition of self vs non‐self were studied in patients with documented Hirschsprung's disease. Monoclonal antibodies reactive with monomorphic determinants of human lymphocyte antigen (HLA)‐A,B,C (Class I) and HLA‐DR (Class II) were used to demonstrate immunohistochemically the expression of MHC antigens in 27 biopsy specimens from a variety of colorectal disorders. The rectal specimens examined from patients with Hirschspmng's disease showed an unexpected, marked elevation of Class II antigens with abnormal localization in the mucosa and lamina propria. This ectopic expression was not seen in any portion of the small or large bowel of patients who did not have Hirschspmng's disease. Furthermore, proximal normal colon of children with Hirschspmng's disease failed to show increased expression of Class II antigen. In an attempt to better define the effector arm at a cellular level, the distribution of helper T cells (CD4⁺), cytotoxidsuppressor T cells (CDS⁺) and natural killer cells (NK; CD16⁺) was examined in 5 cases. In Hirschsprung's disease, rectal infiltration of CDS⁺ and CD16⁺ cells was found, but not CD4⁺ cells. Ectopic expression of Class II antigen with increased numbers of rectal T cells and NK cells suggested that an early immunologic event may be causal in Hirschspmng's disease.