IgA‐containing plasma cells in the lamina propria of the gut: failure of a thoracic duct fistula to deplete the numbers in rat small intestine

Abstract

AbstractThe quantitative importance of the traffic of large lymphocytes through the thoracic duct to the maintenance of the IgA‐containing plasma cell population of the lamina propria of the gut was examined by draining the thoracic duct for periods of time up to 10 days. Contrary to the expectation that IgA‐secreting plasma cell numbers in the small intestine would decline exponentially with a half‐time of approximately 5 days, the numbers of cells remained relatively constant after an initial decline in the first 4 days of lymphatic diversion. Results of in vivo pulse labeling with tritiated thymidine suggest that plasma cell numers are maintained by cell proliferation within the intestinal lamina propria, and that this is a compensatory mechanism brought into play by removal of the normal supply of precursors from the thoracic duct. The compensatory local recruitment of dividing plasma cell precursors principally involves those committed to IgA synthesis. It is suggested that thoracic duct lymph diversion calls into play a local mechanism to make up the deficit of plasma cell precursors lost in the lymph. This may be an accentuation of normal regulation of IgA synthesis in the lamina propria, and suggests that the homing of thoracic duct large lymphocytes is not the only source of renewal of gut plasma cells.