Receptors for human immunoglobulin on acute myeloid leukaemic leucocytes.

Immunoglobulin (Fc) receptors were detected on leucocytes from patients with acute myeloid leukaemia (AML) by rosette formation with human cDE/cDE erthyrocytes (HE) sensitized with Rhesus (Rh) antisera (HEA). Of 7 Rh antisera tested, erythrocytes sensitized with anti-d (Gm10) detected the highest numbers of rosette-forming cells (HEA-RFC) in normal and AML leucocyte preparations. Using this assay, HEA-RFC was studied in 22 untreated AML patients and ce assay detected 11-6% lymphocyte and 2-1% granulocyte HEA-RFC in normal peripheral blood. Leucocytes from 16 to 22 AML patients had a similar or lower percentage than normal lymphocyte HEA-RFC, which could be explained by the dilution of peripheral blood leucocytes by poorly or non-rosetting leukaemic blasts. Ten of these 16 patients were diagnosed as having acute myeloblasts leukaemia. Six of the 22 AML patients had high HEA-RFC values of which 5 were diagnosed as having myelomonocytic leukaemia. Cytocentrifuge preparations of HEA-RFC showed that the proportion able to form rosettes was lower in myeloblasts than in monoblasts. Enzyme treatment (pronase), inhibition or simultaneous labelling of surface Ig and Fc receptors showed that the characteristic surface Ig found to AML cells is, at least in part, bound to Fc receptors. The HEA-RFC test described in this paper could be useful in the immuno-diagnosis of myelomonocytic leukaemia.