GRAFT‐VERSUS‐HOST REACTIONS MEDIATED BY A THYMUS‐BONE MARROW COMBINATION, SPLEEN CELLS, AND LYMPH NODE CELLS FROM AMYLOIDOTIC AND NONAMYLOIDOTIC MICE

GVH-reactions were induced in (C3H × St/A) and (C3H × Balb/C) hybrids by lymph node cells, spleen cells and a thymus-bone marrow mixture from C3H mice during the development of casein-induced amyloidosis. The capacity of the thymus-bone marrow mixture to induce GVH-reactions was totally abolished already after ten injections of casein, when the animals not yet are amyloidotic. This reduction in GVH-reaction could be restored by thymus cells from untreated donors but not by normal bone marrow cells. After 30 injections of casein, no GVH-activity could be detected in the spleen cells and after 40 injections the GVH-activity of the lymph node cells was only half the normal value. Only the bone marrow cells were unaffected by the casein treatment. Using quantitative comparison of GVH-activity of normal thymocytes and thymocytes from donor mice treated with casein alone or in combination with Cortisol, parallel line assay showed that the decrease in the capability of thymus cells from casein treated donors to induce a GVH-reaction was due to a 85 per cent reduction in the number of Cortisol resistant thymocytes. The results are discussed in the light of earlier observations on defects in the cellular immune apparatus of mice undergoing casein-induced amyloidosis.