A surrogate 15 kDa JCκ protein is expressed in combination with μ heavy chain by human B cell precursors

Abstract

A novel κ protein, encoded by a germline JCκ transcript, is expressed by normal and leukemic human B cell precursors. The transcript displays an open reading frame initiated by a non-AUG codon, and predicts a 15 kDa molecule which could be readily confirmed by in vitro translation. Cellular expression was demonstrated by immunofluorescence, precipitation and Western blotting. Furthermore, 2-D gel electrophoresis revealed that germline JCκ can covalently associate with μ heavy chain at the surface of pre-B cells. We therefore propose that during B cell lymphopoiesis, two alternative pathways could be operative in which μ heavy chain can either associate with λ5 or germline JCκ.