Expression of surrogate light chain receptors is restricted to a late stage in pre-B cell differentiation.

Surrogate light chain (psi LC) genes are transcriptionally active in progenitor B (pro-B) cells before immunoglobulin genes are rearranged. Current hypothetical models suggest that the psi LC proteins may couple with surrogate or conventional heavy chain proteins to form cell surface receptors that signal the progressive differentiation of pro-B, precursor B (pre-B), and immature B cells. Monoclonal antibodies were produced and used to examine the synthesis, expression, intermolecular interaction, and function of psi LC during B cell differentiation. The results indicate that, while psi LC production spans several developmental stages, cell surface expression is confined to a relatively late stage in normal pre-B cell differentiation, during which receptor cross-linkage does not impede cell growth or B cell differentiation.