Assembly of the truncated immunoglobulin heavy chain D mu into antigen receptor-like complexes in pre-B cells but not in B cells

Rearrangements of the IgH locus with J(H) joined to reading frame 2 of D-H are greatly underrepresented in B cells. These rearrangements encode the truncated heavy chain D mu. In pre-B cells, we found D mu protein expressed on the cell surface and assembled into a complex with surrogate light chains, Ig alpha, and Ig beta. Cross-linking of either mu m- or D mu m-containing pre-B cell receptors triggered signal transduction reactions. In contrast, when expressed in mature B cell lines, D mu was not detected on the cell surface and did not efficiently bind K immunoglobulin light chains, but did associate with Ig alpha and Ig beta. These results characterize the interactions of D mu chain with other components of the B cell antigen receptor complex and suggest possible mechanisms by which D mu expression may interfere with B cell development.