THE DISTRIBUTION IMMUNOGLOBULIN-CONTAINING CELLS AND T LYMPHOCYTE SUBPOPULATIONS IN THE MOUSE MAMMARY GLAND: A MORPHOMETRIC AND IMMUNOHISTOCHEMICAL STUDY
The distribution of immunoglobulin (Ig)-containing plasma cells and T lymphocyte subpopulations in the mouse mammary gland was studied in different stages of the reproductive cycle using immunohistochemical techniques. Generally, Ig-containing plasma cells (IgA, IgG and IgM) in the mammary gland were few during pregnancy. They gradually increased in number during lactation, further increased in the first 2 days of the post-weaning period, and then quickly decreased. The rich existence of plasma
... existence of plasma cells after the suckling period suggests that their main role is the protection of the mammary gland rather than the transference of passive immunity to neonates. IgA-containing plasma cells were the most frequent isotype, while IgG-and IgM-containing cells were much less throughout the reproductive cycle. In contrast to the plasma cells, T lymphocytes were observed to increase markedly in late pregnancy, while they gradually decreased during lactation, a further decrease being recognizable in the post-weaning period. CD8+ cells, the predominant cell type among T cells, preferentially existed within the epithelia of the alveoli and ducts, whereas CD4+ cells were mainly located in the connective tissue areas. The difference in the dynamics of plasma cells and T lymphocytes suggests that the mammary gland T lymphocytes may lack an isotype-switching role for plasma cells.