Lack of correlation between the effects of cortisone on mouse spleen plaque-forming cells and circulating anti-sheep red blood cell haemolysins.

The effect of 5.5 mg of cortisone acetate given to adult mice 1 day prior to the injection of 4 × 108 sheep erythrocytes was studied. This drug is able to suppress more than 95 per cent of splenic plaque-forming cells (PFC) compared with immunized animals not treated with cortisone. However, the anti-sheep red cell haemolytic titre in the blood was not affected. Several hypotheses to explain this paradox were tested experimentally. Plaque-forming cells in the bone-marrow of cortisone-treated mice, instead of being suppressed, increased to more than ten times their number compared with the controlled animals.