The effect of isoantibodies on red-cell survival.

Abstract

SummaryThis paper reviews the progress in relating in vitro characteristics of isoanti‐bodies, such as Ig class, ability to bind complement, and serum concentration, to the rate of destruction of incompatible red cells that they bring about in vivo.In man, those IgG antibodies that do not bind complement, e.g. anti‐Rh, bring about clearance predominantly in the spleen; in the absence of the spleen, the cells are cleared 100 times more slowly. In the rabbit, with a relatively smaller and evidently less efficient spleen, the minimum concentration of IgG, noncomplement‐binding antibody (anti‐HgA) required for clearance of a dose of 0.02 ml red cells/kg is about 100 times greater than in man.In detecting the presence of low concentrations of anti‐Rh, estimation of the rate of clearance of a small dose (0.02 ml/kg of red cells) is about ten times more sensitive than the indirect antiglobulin test, even after modifying this test to increase its sensitivity.Those IgG antibodies that bind complement bring about far more rapid clearance than those that do not, and IgM antibodies are more efficient still. If noncomplement‐binding antibodies are compared, the ratio of IgM:IgG molecules required for a given rate of clearance is less than 1:100.When small amounts of incompatible red cells are injected into recipients whose serum contains a low concentration of IgM antibody, two‐component curves of destruction are observed. There is evidence that this is due partly to heterogeneity of antigen within the red‐cell population, but that probably the major factor is the limited amount of antibody available.In man, when relatively small volumes (1‐10 ml) of red cells are transfused to previously untransfused subjects, evidence of primary immunization in the form of accelerated destruction of red cells, beginning at 10‐20 days after transfusion and leading to virtually complete clearance of the cells within 30 days, is observed in approximately 30% of recipients. Although it is postulated that this kind of red‐cell‐survival curve (collapse curve) is due to the production of small amounts of isoantibody, no antibody can, as a rule, be detected serologically, and its specificity is a matter for speculation. Experiments in rabbits show that, as in man, collapse curves are less frequently observed when relatively large volumes of red cells are transfused.