Cellular determinants of mammary cell-mediated immunity in the rat. I. The migration of radioisotopically labeled T lymphocytes.

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Abstract
Current theories about the cellular basis of mammary gland immunity are based primarily on the migratory behavior of B lymphocytes bearing intracytoplasmic IgA. These B cells presumably constitute an intestinal pool that circulates independently of the peripheral B cell pool and provides a source of plasma cell precursors for secretory tissues. The hypothesis of a common, yet independent, mucosal immune system has not been applied to mammary gland cell-mediated immunity (CMI). The present study was undertaken, therefore, to compare the migration of T lymphoblasts from gut-associated mesenteric lymph nodes (MLN) with that of their counterparts recovered from cervical lymph nodes (CLN). When labeled with 3H-thymidine and adoptively transferred to lactating recipients, MLN and CLN T lymphoblasts demonstrated equal affinities for the mammary glands. This result suggests that the mammary gland can draw from both circulating pools of T cells (intestinal and peripheral). T cell migration to the mammary gland was found to increase 7- to 10-fold with the onset of lactation and remained high during the first 2 wk postpartum. Activation of MLN and CLN T cells by preculture with Con A greatly increased the proportion of large cells but not alter cell accumulation in mammary tissues. These results, discussed in the context of recent observations regarding T cell locomotion and circulating lymphocyte subsets, suggest that CMI in the mammary gland may not depend solely on oral immunization for its immunologic specificity.