NORMAL PRE-B CELLS EXPRESS A RECEPTOR COMPLEX OF MU HEAVY-CHAINS AND SURROGATE LIGHT-CHAIN PROTEINS

Precursors of B cells, which constitute a subpopulation of the lymphocytes in bone marrow, can be identified by their surface expression of nonimmunoglobulin markers and the absence of immunoglobulin-kappa and lambda-light chains. Most pre-B cells synthesize mu-heavy chains but, without light-chain partners, these undergo rapid cytoplasmic degradation. In the present study, we demonstrate that late stage pre-B cells, like their neoplastic counterparts, express low levels of a surface receptor composed of mu-chains paired with a surrogate light-chain complex formed by Vpre-B and lambda-5-like proteins. The data define a previously suspected but unrecognized stage in normal pre-B-cell differentiation. Expression of a clonally diverse receptor renders this population of immature B-lineage cells potentially vulnerable to clonal selection by antigens and idiotypic interactions.