Pattern of Cellular Alloreactivity of the Solitary Ascidian,halocynthia Roretzi, in Relation to Genetic Control

The pattern of cellular alloreactivity in the solitary ascidian, Halocynthia roretzi (Drashe), was examined using 435 combinations of 30 individuals. A high level of polymorphism was revealed and no two individuals had identical histocompatibility even though they were sampled in a relatively small area of Mutsu Bay. In H. roretzi, the allogeneic reaction seems to be triggered by an absence of common self markers, as in the colony fusibility of B. primigenus, rather than by a specific reaction to non-self markers as in higher vertebrates. We analyzed the allelic compositions of 30 animals assuming that a non-reactive pair share an allele. Since at most four "alleles" are carried by each individual, the solitary ascidian most probably has two genes that control alloreactivity.