Human Membrane‐bound C3 Receptors I. Serological and Immunohistological Demonstration of C3 Receptors

Abstract

The aim of the present study was to present further evidence of the specific reactivity of an anti-C3 receptor serum (AC3RS), to demonstrate membrane-bound C3 receptors by using this AC3RS in different serological an immunohistological methods, and to investigate the relationship between membrane-bound C3 receptors and alpha1-antitrypsin. The AC3RS, or F(ab')2 fragments of the IgG fraction of this antiserum, stained a percentage of various viable cell populations roughly equivalent to the number of cells that bound EAC3b and/or EAC3d; C3 receptor-negative T cells and thymocytes were not stained. On frozen sections of tonsils and kidneys it was found that the AC3RS stained area to which EAC3b adhered. After absorption with neutrophils or Ehu, the AC3RS inhibited the agglutination of EAC3d with tonsil cells, but not the agglutination of tonsil cells or neutrophils with EAC3b; this absorbed AC3RS still stained tonsil cells but not neutrophils, and in frozen tonsil sections it stained only those areas to which EAC3d adhered. The absorbed AC3RS did not stain glomeruli. Antisera to alpha1-antitrypsin failed to inhibit EAC agglutination with C3 receptor-bearing cells or to stain C3 receptor-positive cells either in suspension or in frozen sections. Absorption of th AC3RS with purified alpha1-antitrypsin did not affect its specific reactivity.

The Epstein-Barr Virus Receptor is Distinct from the C3 Receptor

“…Wells et al, unpublished results). Using monospecific antisera against C3 receptors (C 3 b, C3bi, and C 3d) Gerdes et al, 1982;Stein et al, 1981), we analysed the nature of this unusual receptor. Additionally, the properties of the dual-virusspecific EBV receptor were investigated in terms of C3 receptors.…”

“…The ceils were pelleted and washed, then the radioactivity of the pellet and supernatants was measured independently. Various amounts of anti-C3 receptor serum Stein et al, 1981) were incubated with the target cells for 30 min at 37 °C before performing a virus-binding assay. The effects of the anti-C3 receptor serum on EBV binding were directly quantifiable.…”

“…Directly blocking C3 receptors with receptor-specific antibodies would minimize the steric factor. Polyvalent sera which recognizes all C3 receptors, C3b, C3bi, and C3d Gerdes et al, 1982;Stein et al, 1981), were employed to eliminate virus binding. One ~tl serum/106 Raji cells reduced the binding of FITCconjugated C3 and EAC-rosettes by more than 90~ (data not shown).…”

Epstein--Barr Virus Binding to Virus-carrying Cell Lines is Enhanced in the Presence of C3 and C3d

“…In the absence of C3 the virus binds via the combined efforts of two large glycoproteins, thereby implying a large acceptor complex as the cell surface receptor (Wells et al, 1982b). The C3d receptor has also been shown to be a large complex Stein et al, 1981). Thus, the association between the two need not occur at the active sites.…”