Idiotypic relationship of anti‐Ia.2 antibodies

Alloantiserum and hybridoma-derived anti-Ia antibodies were investigated for their idiotypic similarity using 4 monoclonal anti-idiotypes raised against monoclonal anti-Ia. With one anti-idiotype, idiotypic cross-reactivity could be found between three independently derived monoclonal BALB/c anti-Ia antibodies, all of which were directed against the same serological determinant, Ia.2. The respective idiotype, tentatively designated Ia.2 idiotope, could also be demonstrated on anti-Ia.2 antibodies in BALB/C alloantisera, but not on anti-Ia against other specificities. The expression of the Ia.2 idiotope is linked to the Igh allotype; the use of Ig-recombinant mice allowed us to map the Igh-Ia.2 locus to the left of the T15 marker in the Igha V region.