Cross‐reactivity of the NPa and NPb idiotypic responses of BALB/c and C57BL/6 mice to (4‐hydroxy‐3‐nitrophenyl)acetyl (NP)

Abstract

A comparative antigenic analysis was carried out to determine whether cross‐reactivity exists between the major idiotypic responses to (4‐hydroxy‐3‐nitrophenyl)acetyl (NP) in BALB/c and C57BL/6 mice. Extensive cross‐reactivity exists between the NP^a (BALB/c) and NP^b (C57BL/6) allotype‐linked idiotypic responses to NP. The cross‐reactive determinants of the NP^b idiotype are confined to one particular group of NP^b‐positive monoclonal antibodies. The extent of cross‐reactivity between this group of C57BL/6 antibodies and idiotype‐positive monoclonal antibodies of BALB/c is so great that they cannot be readily distinguished as NP^b‐ or NP^a‐positive antibodies with polyclonal anti‐idiotypic reagents. That this cross‐reactivity is not unique to monoclonal antibodies was confirmed by the demonstration of these cross‐reactive determinants in the immune sera of individual BALB/c and C57BL/6 mice. Additionally, evidence was obtained from these experiments and from earlier ones from this laboratory which suggests that the BALB/c idiotypic response to NP‐protein conjugate is more homogeneous than the C57BL/6 idiotypic responses.