Early increase in graft-versus-host reactivity during pregnancy in the mouse.

Alloreactive T levels of para-aortic lymph nodes (PALN) and spleen were determined on different days of pregnancy in BALB/c females by local and systemic graft-versus-host (GvH) assays. A significant increase in GvH reactivity was registered early in both allogeneic and syngeneic matings, operating not only towards paternal but also towards third party strains. Immunoregulatory mechanisms in PALN also involved the appearance of progressive suppression during the first days of pregnancy. The possible role of non-specific early increases in T alloreactivity in triggering suppressor mechanisms and the nature of the immunogens responsible for the alterations in GvH reactivity are discussed.