title: IgG receptors on foetal chick yolk sac.
abstract: In the chicken, maternal IgG is deposited in the oocyte yolk and subsequently transported intact by the foetal chick yolk sac into the chick circulation. Such transport appears to require a specific membrane-localized IgG receptor. Using the assay of 125I-yolk IgG binding, we have investigated the existence and properties of such receptors in yolk sac tissue disks. We find that: (1) There are specific, 125I-IgG binding sites on yolk sac tissue; (2) specific yolk 125I-IgG binding has a distinct pH optimum at pH 6.0--6.3; (3) the apparent equilibrium dissociation constant of specific 125I-IgG binding is 2--3 X 10(-6) M; and (4) heterologous proteins compete less efficently than yolk IgG for 125I-IgG binding.
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D001665:Binding Sites; D002642:Chick Embryo; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G; D013997:Time Factors; D015017:Yolk Sac / Q000276:immunology*
chemical_list: D007074:Immunoglobulin G