Development of specific antibody and in vivo response to antigen in different rat strains: effect of dexamethasone and importance of endogenous corticosteroids.

Endogenous glucocorticoids undoubtedly play a role in the control of immune responses: their contribution to inter-strain variation is unknown. The development of specific IgG and IgE was measured following inoculation with ovalbumin in Lewis, Fischer, Wistar and Brown Norway rats. The Lewis gives a smaller IgG and IgE response than the other strains and the response in vivo to antigen injected into the paw correlates with the titre of specific antibody. Treatment with the steroid receptor antagonist RU486 (mifepristone) following inoculation reveals that in the Lewis, and to a lesser extent in the Brown Norway, the development of a specific IgG response is limited by endogenous corticosteroids. The IgG response in different strains is differently sensitive to treatment with the synthetic glucocorticoid dexamethasone, the Lewis being particularly resistant. The importance of control by endogenous corticosteroids should not be overlooked in contributing to strain differences in immune response.