Variable region structure and staphylococcal protein a binding specificity of a mouse monoclonal IgM anti-laminin-receptor antibody

Abstract

Staphylococcal protein A is a cell wall-attached polypeptide that acts as a B-lymphocyte superantigen. This activation correlates with specific V(H) gene segment usage in the B-cell receptor. B-cell receptor assembled from members of the V(H)3 family in humans, or S107 family in mice, has an intrinsic affinity for protein A. Human V(H)3-derived antibodies bind to domain D of protein A. We have characterized a mouse IgM monoclonal antibody that binds protein A. The sequencing of the variable region suggests an almost germline-encoded V(H) derived from S107 family and a V(K)8-derived V(L). The binding specificity of the monoclonal antibody was tested with various recombinant constructions derived from protein A. We show that, unlike human V(H)3-derived antibody, mouse S107-derived immunoglobulin binds to the B domain of the bacterial superantigen.