An analysis of the 4c complex of HL-A based on Indian populations.

Sera detecting part or all of the 4c group of HL-A antigenic specificities were compared in two American Indian populations, the Ixils and the Pimas, and in one Spanish-Indian hybrid population, the Mestizos of Peru. Several new variants appeared. These were not identical to HL-A5, W5 or W18. Two of the variants appeared to represent specificities Z57 and Z51 as described during the 1972 Histocompatibility Testing Workshop. In addition, three new specificities could be detected. These were Z42, Ao88 and Ao93. Z42, Ao88 appeared to belong to the 4c complex and Ao93, a new specificity of the second locus, may belong to this same cross-reactive group.