An idiotope expressed on a monoclonal antibody specific for human haemoglobin beta chain and naturally occurring immunoglobulin(s)

HId-1A (γ₁:κ), HId-2a (μ:κ) and HId-4a (γ:1:κ) monoclonal anti-idiotopes of BALB/c origin were induced by the human haemoglobin-reactive, B10.D2-derived monoclonal antibody Hb-2d. HId-1a and HId-4a seem to react with the same idiotype and may, in fact, be encoded by the same V, D and J genes. HId-2a, on the other hand, seems to react with an idiotope different from that recognized by the other two anti-Id's and present in the sera of non-immune B10-H-2 congenic mice. HId-2a, but not HId-1a or HId-4a, may react with an idiotope in or near the antigen binding site of Hb-2d. Naturally occurring immunoglobulin carrying the HId-2a idiotope was affinity-purified from the pooled sera of B10-H-2 congenic mice and partially characterized. It possesses primarily the γ(2b) heavy chain, but small amounts of γ₁, γ(2a) and μ heavy chains are also detectable. The κ and λ light chains are both present in significant amounts. In addition, the affinity-purified immunoglobulin is unreactive with human haemoglobin, is not a rheumatoid factor and does not expreess in detectable amounts the idiotope recognized by HId-1a and HId-4a. It is possible that all or some part of this polyclonal reagent is specific for antigens normally present in the environment.