Hydrocortisone Resistance of Activated Initiator Cells in Graft versus Host Reactions

Abstract

ALTHOUGH corticosteroids are usually considered to be lympholytic and immunosuppressive, some immunocompetent cells, presumably lymphoid, resist the actions of corticosteroids; for example, the graft versus host cell in chicken1 and mouse2 thymus, and the bone narrow antibody-forming cell precursor3. We have shown4 that the cell(s) in mouse spleen which can initiate graft versus host (GVH) reactions are resistant to the action of hydrocortisone. In these experiments, hydrocortisone was given to normal mice of parental strains. Two days later the surviving spleen cells (about 20%) were transferred to adult F1 hybrid recipients, where they showed unimpaired GVH responses as measured by splenomegaly. In these circumstances, the GVH initiator cell was exposed to hydrocortisone before coming into contact with antigen (mainly H2), and it was thus unlikely to be dividing rapidly, if at all5. Because there is evidence that corticosteroids have their greatest effects on rapidly dividing cells6,7 we have investigated the hydrocortisone sensitivity of GVH cells during antigenic stimulation, when thymus-derived cells are known to proliferate8,9.