Mechanism of Eosinophilia. VII. EOSINOPHILIA IN RATS WITH LYMPHOMA

S ummary Inbred rats developed an increased blood eosinophil count 2 weeks after injection of syngeneic or semi‐syngeneic lymphoma cells. An eosinophilia did not occur in allogeneic recipients. Autoradiographic studies of bone marrow eosinophil production showed that additional eosinophils were not being made, and tissue eosinophil levels were also normal. Moreover injections of prednisolone did not lower blood eosinophil counts significantly in the rats with the lymphoma. Other experiments showed that the eosinophilia was probably not due to a graft‐versus‐host reaction. It was concluded that the mechanism of eosinophilia was a prolongation of eosinophil survival in the blood, possibly due to blockage of normal emigration pathways into tissues, by large numbers of blood‐borne lymphoma cells.