Human Monocytes: Distinct Receptor Sites for the Third Component of Complement and for Immunoglobulin G

Abstract

Human monocytes contain two distinct receptor sites, one specific for the third component of complement (C'3), the other for immunoglobulin G(gammaG). The two receptors may function either independently or cooperatively in the induction of phagocytosis. Ingestion of erythrocytes coated with immunoglobulin M antibody requires a relatively large number of bound C'3 molecules per cell. Ingestion of erythrocytes sensitized with gammaG antibody is independent of complement; however, the reaction is inhibited by concentrations of gammaG far below those in normal serum. Inhibition by gammaG-globulin is overcome by a relatively small number of bound C'3 molecules per cell. The two monocyte receptors exert a cooperative effect on ingestion by monocytes of erythrocytes coated with gammaG antibody in the presence of inhibitory amounts of free gammaG.

The Relationship Between Group a and Group C Meningococcal Polysaccharides and Serum Opsonins in Man

“…Observations on complement requirements for erythrophagocytosis by polymorphonuclear and mononuclear leukocytes have demonstrated that for efficient phagocytosis of red cells, 7S antibody and the first four components of complement are required (21,22). Phagocytosis of pneumococci in the presence of type-specific opsonins and heat-labile factors has recently been reported by Johnston, Klemperer, Alper, and Rosen (23).…”

Binding of Soluble Immune Complexes to Human Lymphoblastoid Cells

“…According to these authors, complement bound to the antibody within the complexes may sterically hinder or directly bind to the sites on the Ig molecules which have affinity for the lymphocyte membrane. Although soluble aggregates containing complement bind to cells primarily via complement receptors, it should be noted that in other systems it has been shown that receptors for IgG Fc play a significant role in other cell functions such as phagocytosis of EAC' (33,34).…”

Immunologic characterization of the mononuclear cell infiltrates in rheumatoid synovia, in rheumatoid nodules, and in lip biopsies from patients with sjö;ugren's syndrome

“…Recent developments in the field of cellular immunology have now permitted differentiations of different types of mononuclear cells (1)(2)(3)(4)(5)(6)(7). Human lymphocytes may be classified, based upon animal experiments and studies in patients with immunodeficiency states, into at least two groupsthymic-dependent lymphocytes (T cells) and thymicindependent or bone marrow-derived lymphocytes (B cells) (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). T cells are thought to mediate reactions of cellular immunity, whereas B cells are primarily concerned with humoral immunity (14,15).…”