The Production of Anti HL‐A Cytotoxic Antisera Through Planned Immunization by Intravenous Injection of Small Aliquots of Whole Blood

Planned immunizations were performed in 20 pairs of unrelated individuals. The immunization procedure, employing weekly injections of small aliquots of whole blood, was shown to be safe and adequate to elicit an anti‐HL‐A response in the great majority of cases. The antibody responses showed two sharply distinguishable patterns: “Restricted”, with the production of monospecific, non cross‐reacting antibody; and “Broad → Restricted”, with the production of an antibody reacting against specificities other than those possessed by the donor, and becoming more and more restricted with time. Both patterns are constantly reproduced upon subsequent stimulations. The pattern of response appears to be determined primarily by some peculiarity of the donor's specificity(ies) or by some characteristic relationship between donor and recipient antigenic constitution, rather than by a special reactivity of the recipient per se.