Further Observations on Isosensitization to the Rh Factor

Abstract

Summary

The results of experiments on sensitization of male type rh individuals by intravenous injections of Rh₀-positive blood at intervals of 3 to 4 months are described. Of 47 subjects receiving 2 injections, 38.3% became sensitized; after 3 injections, the incidence of sensitization rose to 54.4%; after 4 injections, the percentage rose to 63.5%, while after 5 injections the incidence of sensitization was 67.2%. Because of the small number of individuals receiving more than 5 injections, it is not possible to state with certainty whether the incidence of sensitization approaches a maximum limit somewhere between 70 and 80% of individuals injected, or whether all individuals eventually would become sensitized providing they are given a sufficient number of injections. In any event, it is obvious that the deliberate injection of Rh-positive blood is a potent means of sensitizing Rh-negative individuals.

In contrast to these results, not one among 19 type Rh₁ Rh₁ individuals receiving repeated injections of type rh blood became sensitized to the Hr factors. These results confirm the conclusion based on clinical observations that the Hr factors are much weaker antigens than the Rh factors.