Cytochemistry of gamma-glutamyltransferase in haemic cells and malignancies.

An improved cytochemical method for the demonstration of gamma-glutamyltransferase is described. The enzyme was demonstrated in almost all normal leucocytes and in platelets. There was markedly reduced activity in most lymphoproliferative disorders. In a single case of Hodgkin's disease, T-lymphocytes showed slight to moderate activity contrasting with the marked activity displayed by Reed-Sternberg cells. The plasma cells of multiple myeloma and plasma cell leukaemia showed activity equal to or stronger than that of their normal counterparts. In acute myeloid leukaemia the positivity varied widely in blast cells, but was consistently increased in monoblasts of acute monoblastic leukaemia. gamma-Glutamyltransferase may serve as a differentiation marker in the study of granulocytic and lymphocytic cell lineages.