Receptors for Complement and Immunoglobulin on Human and Animal Lymphoid Cells

The mononuclear cells participating in immune responses are heterogeneous both morphologically and functionally. During the past few years a number of receptors and differentiation antigens have been identified on different immunologically competent cells. The presence or absence of these receptors on mononuclear cells of unknown type may provide information as to their origin. Bone marrow derived (B lymphocytes) can be identified by the presence of easily detectable surface immunoglobulin (Raff 1970); most B lymphocytes also have a receptor for antigen-antibody-complement complexes which is detected by using red cells (E) coated with antibody (A) and complement (C) (Bianco et al. 1970). B lymphocytes can also be identified by the presence of a receptor for he F^ portion of immunogiobulin G (Basten et al. 1972a,b) which can be detected with antigen-antibody complexes, or by using fluorescein-labeled aggregated gamma globulin (Dickler & Kunkel 1972). In the mouse, thymus derived (T lymphocytes) can be identified by the presence of the theta iso-antigen; in man, most T lymphocytes form non-immune rosettes with sheep red blood cells by as yet unknown receptors (Lay et al. 1971, Jondal et al. 1972). It has also been possible to identify human T cells (WilUams et al. 1973) by the use of heterologous anti-thymocyte sera which have been rendered specific for T cells by absorption with a pure population of B cells. Cells of the monocytemacrophage series also bear a receptor for EAC (Huber et al. 1968) and