Sheep red blood cell receptor and the epitope detected by Leu-5 monoclonal antibody in primates.

The expression of the epitope detected by the monoclonal antibody Leu-5 and the rosette formation with sheep red blood cells was examined for the mononuclear cells of 25 primate species including human subject. The plot of rosette-forming cells against Leu-5-positive cells enabled us to classify these species into three large groups: hominoids--Old World monkeys (Leu-5-positive cells greater than or equal to rosette-forming cells), New World monkeys (Leu-5-positive cells less than rosette-forming cells), and prosimians (Leu-5-positive cells less than 5%, some of them with both Leu-5-positive cells and rosette-forming cells less than 5%).