SURROGATE LIGHT-CHAIN PRODUCTION DURING B-CELL DIFFERENTIATION - DIFFERENTIAL INTRACELLULAR VERSUS CELL-SURFACE EXPRESSION

Expression of the surrogate light (psi L) chain genes encoding the Vpr eB and lambda 5/14.1 proteins is restricted to B lineage cells, Pro-B and pre-B cells produce psi L chains, but whether both employ these as cell surface receptor components remains enigmatic. Recombinant human VpreB protein was used to generate a large panel of monoclonal anti-V preB Abs to examine this issue. Native psi L chain proteins within pro -B cells as web as those serving as receptor components on pre-B cells were precipitated by 16 of the 26 anti-VpreB Abs. Surrogate light cha ins were easily detected on pre-B cell lines! whereas these anti-VpreB Abs reacted with pro-B cell lines only after plasma membrane permeabi lization. The subpopulation of normal bone marrow cells bearing pre-B receptors included large and small pre-B cells exclusively, although p ro-B cells also contained intracellular VpreB, VpreB proteins were not detected on or within B cells in bone marrow or the circulation, but a subpopulation of B cells in germinal centers was found to express th e VpreB proteins intracellularly. Surrogate I, chains are thus intermi ttently produced during human B-lineage differentiation, while their r ole as receptor components appears limited to the pre-B cell stage.