Colostral cell-mediated immunity and the concept of a common secretory immune system.

Historically colostrum and milk have been thought to confer immunity on the neonate only by virtue of their immunoglobulin content. Recently we have observed that colostrum also contains viable T lymphocytes capable of expressing cell-mediated immunity in vitro and have employed techniques of lymphocyte culture to elucidate the local nature of mammary tissue immunity at the T-cell level. The results indicate that the activity of colostral lymphocytes appears not to represent the total immunological experience of the mother but that they may contain reactive clones beneficial for the suckling. Colostral immunity appears to depend upon sensitizing events within the intestine and respiratory tract, followed by the migration of lymphoid precursors to the breast, suggesting a relationship between the expression of immunity at various secretory surfaces.