International Immunology, Vol. 1, No. 4, pp. 355-361,September 1989
© 1989 Japanese Society for Immunology
Mu heavy chains can associate with a pseudo-light chain complex (
L) in human pre-B cell lines
Department of Microbiology and Division of Developmental and Clinical Immunology, University of Alabama at Birmingham Birmingham, AL 35294, USA
Correspondence to: 1Current address Department of Tumor Cell Biology, St Jude Children's Hospital, Memphis, TN 38101, USA
Correspondence to: Correspondence to. Dr William G Kerr, S-337, Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
In pre-B cells, the earliest identiflable stage of B cell differentiation, there is an asynchrony of Immunoglobulin chain expression in that µ heavy chains are synthesized in the absence of light chain synthesis. These µ chains largely remain intracellular and are degraded. Here we demonstrate that a fraction of µ chains in human pre-B cell lines can reach the surface in association with three pre-B-specific proteins with relative molecular masses of 22, 18, and 16 kd, which we term collectively the pseudo-light chain complex, 
L. This association generates a multimeric complex, µ2–L. Two of the L proteins (22 and 16 kd) are 
-Immunoreactive and form disulfide bonds with µ chains, suggesting that they are closely related to conventional light chains. The 18 kd L species is a non-covalently-assoclated member of the complex. The expression of µ–L complexes on the surface of pre-B cells could have a functional role in the control of pre-B growth and differentiation by the hematopoletic microenvironment.
Keywords: acute lymphoblastic leukemia, B cell differentiation, BiP, light chain, surface µ chains
Received 4 May 1989, accepted 15 May 1989.