Neely, Brian C.

Abstract The I-E and I-C subregion products have been identified specifically in haplotypes H-2k and H-2d. Haplotypes H-2p and H-2r are assumed to express products of I-E/I-C subregion on the basis of cross-reactions with anti-I-Ek sera. Anti-I-Ek or I-Ed sera do not cross-react with haplotypes H-2s, H-2b, H-2q, and H-2f. Specific immunizations to produce anti-I-Eb and anti-I-Es alloantisera have been unsuccessful. We turned to xenoimmunization to serologically identify the gene products of this chromosomal segment in the above haplotypes. NP-40 detergent solubilized antigenic material mixed in Freund's complete adjuvant were immunized into rabbits. Two weeks later a booster was given and the rabbits bled one week later for antisera analyses. The rabbits were then boosted once a month and bled periodically. The rabbit antiserum reacted with all mouse strains. Absorptions with appropriate recombinants showed the presence of specific antibodies against the I region products. For example, rabbit anti-B10 serum after absorption with B10.A (3R) left residual activity against B10.A (18R), suggesting antigen(s) mapping between I-J and H-2D. The antiserum was further absorbed with B10.F (13R) to make it specific for I-E/IC subregions. Rabbit anti-B10.M sera, after absorption in ATFR.1 reacts with ATFR.5, suggesting activity in the K and I regions. Since absorption with platelets did not remove activity for spleen cells, presence of anti-If antibodies is suggested. Sequential immunoprecipitation analysis will be performed to screen for anti-I-E/I-C antibodies. Rabbit anti-B10.G and Rabbit anti-B10.S sera are currently being analyzed for I region activity.