Lymphocytotoxins in leukaemia.

Fifteen out of 51 patients with leukaemia have produced a lymphocytotoxin in their serum which reacts with their own and a high percentage of all other lymphocytes. This is probably a protein, but not an antibody. It has been detected only before or early during cytotoxic treatment, or during a relapse. It is postulated that the lymphocytotoxin is a specific protein produced by the leukaemic cells, which may facilitate their spread in the body.