The Fc receptors of normal and cancer patients monocytes.

The ability of human monocytes from normal donors and gastric-cancer patients to form rosettes with "O" Rh+(D) human erythrocytes coated with hyperimmune IgG anti-D antibody (EAhu) and to kill the same target in antibody-dependent cellular cytotoxicity (ADCC) were assessed. Trypsin pretreatment of normal monocytes decreased their ability to form rosettes with EAhu complexes, but their ADCC activity was unaffected. The Fc receptor (FcR) expression and ADCC activity of monocytes of cancer patients were elevated, and trypsin-treatment led to their further increase. The elevated values were related to the presence of the tumour. These results may suggest that human monocytes possess trypsin-sensitive and trypsin-resistant Fc receptors. The trypsin-resistant FcR seems to be involved in ADCC phenomenon and to be preferentially expressed on monocytes of some cancer patients.