Abstract
To the Editor: Crohn's disease is an inflammatory bowel disease of increasing incidence and unknown origin. Mononuclear-cell infiltration1 of the lesions suggests that immunologic mechanisms may be involved. However, none of the various immunologic abnormalities that have been reported in this disease2 have been directly associated with the mechanisms of the lesions or with disease activity. β2-Microglobulin is a low-molecular-weight protein non-covalently associated with the heavy chain of HLA antigens on cell membranes. Its structure shows a great similarity with immunoglobulin domains. Lymphocyte activation increases the release of β2-microglobulin from both T and B cells,3 and . . .