Assembly of the truncated immunoglobulin heavy chain Dμ 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 Dμ. In pre-B cells, we found Dμ protein expressed on the cell surface and assembled into a complex with surrogate light chains, Igα, and Igβ. Cross-linking of either μm- or Dμm-containing pre-B cell receptors triggered signal transduction reactions. In contrast, when expressed in mature B cell lines, Dμ was not detected on the cell surface and did not efficiently bind κ immunoglobulin light chains, but did associate with Igα and Igβ. These results characterize the interactions of Dμ chain with other components of the B cell antigen receptor complex and suggest possible mechanisms by which Dμ expression may interfere with B cell development.