Human Ia beta chains and the invariant chain share a common antigenic determinant.

We have presented evidence that a mouse monoclonal antibody 1,227, which was previously shown to recognize a determinant on the light chains beta 1 and beta 2 of human Ia antigens, also recognizes a determinant on the invariant chain (1) associated with these molecules. Ia-specific proteins were resolved by two-dimensional (2D) PAGE and electrophoretically transferred onto nitrocellulose filters. The presence of a determinant shared between beta 1, beta 2 and I was established using "Western blotting" technique. In addition, we demonstrated that 1,227 can immunoprecipitate isolated beta 1, beta 2, and the invariant chain proteins following their separate elution from SDS-PAGE.