CR1 and neoplasm: Staining procedure with monoclonal antibodies (moabs) against Mo/M phi revealed different clusters of antigen expression: (1) moabs 27E10 and a-CD35 detected a subgroup of Mo/M phi with particular staining of perivasal Mo; (2) moab a-CD1 stained preferentially cells in tumour cell clusters; (3) moabs that reacted with cells of either typical M phi or dendritic morphology throughout the tumour-tissue: a-Fc gamma receptor I-III, a-class II antigens, a-CD4, Rm3/1, a-CD36 and 25F9.