Elevated CD4 antigen expression among activated T cells in lymph nodes draining mammary regions chronically exposed...

We examined the cell cycle distribution and subset marker characteristics of mucosal-associated supramammary lymph node (MALN) T cell subpopulations at sites proximal and distal to the mammary region of animals repeatedly injected with Staphylococcus aureus antigen. Multiparameter flow cytometric analysis of draining MALNs showed that CD4+ T cells expressed significantly greater amounts of CD4 surface antigen than corresponding cell populations in non-draining MALNs. In contrast, the intensity of CD8 surface antigen expression among draining MALN CD8+ cells remained unchanged. Draining and non-draining MALNs contained nearly equal proportions of large CD4+ T cell subpopulations (CD4/CD8 ratio) with the former having greater cell numbers undergoing active DNA synthesis (S + G2M phase) in vivo. Similarly, draining MALNs had greater cell numbers of small CD4+ lymphocytes in the S + G2M phase, although with lower CD4/CD8 ratios of corresponding cell populations in non-draining MALNs. This study demonstrates that prolonged exposure with Staph aureus antigen enhances the cell number and expression of CD4 surface antigen among T lymphocyte subpopulations actively synthesizing DNA in draining MALNs. The role of the CD4 antigen in inflammatory responses at sites proximal (draining) and distal (non draining) to chronic infection within the mammary/mucosal immune network is discussed.