Isolation and characterization of colonic intraepithelial and lamina proprial lymphocytes.

A technique is described, involving sequential treatment of the human colonic mucosa with EDTA in calcium-magnesium-free medium, and with collagenase, to isolate lymphoid cells enriched for intraepithelial (IEL) or lamina proprial lymphocytes (LPL). The IEL and LPL isolates also contained small numbers of eosinophils, mast cells, neutrophils, and macrophages. Plasma cells were present in the LPL but not in the IEL. The IEL isolates contained approximately equal proportions of T, B, and null cells. In contrast, the LPL suspensions contained 52% of T cells, 22% of B cells, and 26% of null cells. The most prevalent membrane immunoglobulin in the two colonic lymphoid cell suspensions was IgA (IEL--53%; LPL--71%). In colonic tissue sections, the percentages of immunoglobulin-containing cells as well as the proportions of cells containing IgA, both in the epithelial layer and the lamina propria, were similar to those found in the suspensions of lymphocytes stained for membrane immunoglobulin. These and other morphologic and characterization data support the contention that the two colonic lymphoid cell populations, obtained by the isolation procedures, were selectively enriched for intraepithelial or lamina proprial lymphocytes, respectively. Thus, this technique provides an important tool for further studies of the functional properties of the gut-associated lymphoid tissues.