• Red cell immune adherence (RCIA);
  • complement;
  • receptors;
  • immune adherence;
  • assay;
  • immune adherence;
  • immunocyte;
  • red cell;
  • fetal development;
  • pregnancy

ABSTRACT: The addition of autologous serum to mixtures containing human red cells, from pregnant and nonpregnant females, and sheep red cells resulted in the formation of mixed aggregates containing both human and sheep red cells. In contrast, no aggregate formation occurred when autologous cord serum was addded to mixtures containing cord red cells and sheep red cells. Heat inactivation of the adult serum or the presence of 0.15 M EDTA prevented the formation of mixed aggregates. These observations indicated that the mixed aggregates occurred through the complement-dependent red cell immune adherence (RCIA) phenomenon. The addition of untreated cord serum to mixtures containing inactivated adult serum restored the formation of mixed aggregates, indicating that the cord serum contained sufficient complement for RCIA. Natural antibody against sheep red cells was present in adult sera but was absent in cord sera.

Using the RCIA receptor assay, the RCIA receptor activity of cord red cells was found to exceed significantly that of the adult pregnant cells (p < 0.0025). It is postulated that this may represent an aspect of immune adaptation between mother and fetus.