Interaction of nonallelic genes on cellular antigens in species hybrids of Columbidae. II. Identification of interacting genes.

Evidence was presented in a previous paper' that a hybrid substance, encountered after an antigenic character (ch4) of Streptopelia chinensis was transferred to S. risoria, resulted from the interaction of nonallelic genes. Specifically, the cha4 cellular antigen from chinensis showed no hybrid substance when present in backcross individuals that were homozygous for an independently inherited character of chinensis (ch-8/ch-8). In contrast, all backcross individuals with ch-4 invariably showed the hybrid substance in the presence of the ri-8 antigen of risoria, ri-8 being a contrasting character of risoria to ch-8 of chinensis.' In this paper, evidence is given of the dependence of the antigenic specificities of the hybrid substance upon whether the gene for the group4 antigen, following transfer to risoria from each of the four species [ch-4 from chinensis, hu4 from humilis (also called tranquebarica), or4 from orientalis, or se4 from senegalensis] interacts with the gene(s) for ri-8 of risoria, or with that for hu-8 of humilis, or-8 of orientalis, or se-8 of senegalensis. (The genes effecting these five members of the group-8 antigen seemingly form a multiple allelic series.5) The data show that se-4, which behaves genetically as a single character in senegalensis,2' 3 hu4, and or4 within the respective species contain demonstrable antigenic specificities that actually are interaction products. Explanation.-The technical procedures employed in transferring to risoria the respective antigenic characters of both group-4 and group-8 from chinensis, humilis, orientalis, and senegalensis were described or cited in a previous report.' In brief, backcross hybrids, which are distinguishable from risoria birds only in that they possess the ch-4 antigen of chinensis, carry antigenic factors (defghi) in addition to factors abc that characterize ch-4 in chinensis.". 3 Further, the backeross birds carrying only hu-4, or-4, or se-4 to differentiate them from risoria individuals also possess these six specificities.' Thus, the four kinds of backcross birds are indistinguishable in their content of factors of the group-4 antigen. The homozygotes and heterozygotes of these members of group-4 likewise are indistinguishable in that they carry the complete complement of these antigenic specificities, irrespective of the specificities present in the parental species.' Only specificity i for the hybrid substance is peculiar to the backcross birds;l the others are found in various combinations as normal constituents of the cells of other species.3 Despite rigorous search, no contrasting character to those constituting group-4 has been demonstrated in risoria. In this paper a dash following the diagonal (as ch-4/-) indicates that the bird was heterozygous; a question mark (as ch-4/?) indicates that the cells may have come from either a heterozygote or a homozygote. Three antisera provided the reagents that detected the various specificities of the different cells. In Table 1, an antiserum to chinensis, following absorption with the cells of risoria and those of backcross birds with ch-8, contained strong antibodies for ch-4 cells, recognizing antigenic specificities abc3 4 (row 1). A mixture of two antisera (#1 in Table 1) against the cells of backcross birds with ch-4, after absorption by the cells of the two parental species, chinensis and risoria, contained antibodies for antigenic specificities deft (row 3). Absorption of this antiserum with cells of risoria and humilis, orientalis, or senegalensis (provided those of the latter two species carried the group-4 antigen) resulted in a reagent with antibodies for specificity i (row 4). A third antiserum (#2), a mixture of antisera against ch-4/ch-4 and hu-4/cells, respectively, con-