Primary antibody response against K and D regions of the H-2a and H-2d haplotypes

The capacity of D and K antigens of the H-2d and H-2a haplotypes to induce primary IgM response was evaluated in host-donor combinations using congenic recombinant strains of mice. Host animals were immunized with an i.p. injection of 2 X 10(7) allogeneic spleen cells. Direct plaque-forming cells appearing in immune spleens were assayed with cells of lymphomas L2 of strain A and L5178Y of strain DBA/2, and mastocytoma P815 of strain DBA/2, as targets. Serum antibodies were titrated for cytolytic activity with the same targets as above, and with spleen cells of strain A mice. Titration of serum hemagglutinins was performed using A erythrocytes. The following results were obtained: (1) H-2Dd antigens were shown to be more potent in stimulating primary IgM antibody response than were H-2Kk and H-2Kd antigens, as measured by both plaque assay and serum antibody titration. (2) The observed dominance of D antigens of the haplotypes under study did not seem to be dependent on the number of antigenic specificities involved. (3) Comparable results were obtained with both lymphoid and nonlymphoid target cells of either normal or malignant origin.