STUDIES ON CELLULAR ALLOANTIGENS IN THE BLOOD OF HORSES

Lymphocyte alloantigens in horses were investigated using methods developed to study human lymphocyte alloantigens. Five hundred and fifty sera from parous mares and 58 antisera produced by intramuscular immunization were tested for lymphocytotoxic antibodies. All antisera produced by alloimmunization and 80% of the sera from parous mares had lymphocytotoxic antibodies. The data from typing 600 horses was analyzed by computerized cluster analysis. Groups of antisera with highly correlated reaction patterns (r > 0.66) were assumed to recognize a common specificity. These assumptions were supported by absorption tests, lysostripping and family studies. Eleven specificities were identified and designated E1, E2, E3, E4, E5, E8, E9, E10, E11, E12 and E14. Absorption tests demonstrated that these specificities are expressed on lymphocytes and platelets but are not detectable on red blood cells.;Family data indicated that the 11 specificities are gene products of a single system, designated ELA. However, this system may include two loci. For example, the lymphocytes of 9 horses were positive for 3 ELA gene products thereby implicating 2 loci. E10 was always one of those specificities. The specificities on one of the horse's lymphocytes were lysostripped independently of each other, thereby indicating that they are on separate molecules. Further, 4 mares transmitted the gene for E10 in coupling phase with genes for either E3, E5 or E9. Therefore, the ELA system may include 2 polymorphic loci for lymphocyte alloantigens.;Studies involving three families demonstrated that the ELA system is linked to the A blood group system. Lod scores for the three families were 3.61, 3.33 and 4.82 with (theta) = 0. Two recombinant phenotypes were found among 50 progeny, indicating that the recombination frequency between the ELA and A systems is 4%.;The production of hemolysins specific for blood group factors J, Y and D of the D system is also reported. This is remarkable because all previous reports indicated that D system blood factors elicit the production of agglutinins but not hemolysins.;Several subtypic-supertypic relationships between the specificities were apparent from their distribution, absorption studies and lysostrip studies. E1 is subtypic to E10; E2 and E3 are subtypic to E8; E12 is subtypic to E4; E5 may be subtypic to E14; and E9 may be subtypic to E11. No other inclusion groups involving these specificities were apparent.