Cellular determinants of mammary cell-mediated immunity in the rat: kinetics of lymphocyte subset accumulation in the rat mammary gland during pregnancy and lactation.

The present study was undertaken to determine the pattern of T- and B-lymphocyte accumulation in the rat mammary gland during gestation, lactation, and weaning. Adoptive transfer experiments were then used to identify the likely source and extent of immigrating cells during this period. Our results indicate that the mammary gland accumulates levels of cIgA+, W3/13+, and W3/25+ cells that are approximately one third their densities in the small intestine. Cell migration studies suggest that the input of immigrating B-cells is not sufficient to maintain these levels in the gland, and we have suggested that substantial clonal expansion must occur among cIgA+ B-cells within the mammary tissue itself. The migratory behavior of T-cells, their pattern of appearance throughout gestation and lactation, and the predominance of the T-helper cell subset suggest that T-cells regulate B-cell development within the mammary gland.