Hydrocortisone Resistance of Graft vs Host Activity in Mouse Thymus, Spleen and Bone Marrow

Abstract

The effects of corticosteroids on the graft vs host activity of thymus, spleen and bone marrow were studied. Adult BALB/c mice were given 2.5 mg of hydrocortisone intraperitoneally 2 days before killing. The number of nucleated cells in their spleens was 21% of control values; in bone marrow, 79%; and in thymus, only 6%. When equal numbers of thymus cells from hydrocortisone-treated and control animals were administered to neonatal CAF₁ recipients, the hydrocortisone-thymus was by far the more active at initiating the graft vs host (GvH) reaction, as measured by splenomegaly. Similarly, when equal numbers of spleen or bone marrow cells from hydrocortisone-treated or normal mice were transferred to normal adult CAF₁ recipients, the hydrocortisone-spleen and hydrocortisone-bone marrow were significantly more active at initiating GvH. It is suggested that a population of cells which is not involved in GvH is preferentially destroyed by hydrocortisone in each of these organs. The corticosteroid-resistant thymus cells, which have previously been shown to exist in the medulla, thus have characteristics of peripheral lymphoid cells.