Low-molecular-weight (61K) mu chain in P3HR-1 cells and various derived somatic hybrids

The expression of a truncated 61K mu chain in the Burkitt lymphoma lien P3HR-1 and a derived ouabain and TG-resistant subline, PUT, and in various somatic cell hybrids with PUT as one of their parents is described. Both PUT and P3HR-1 contain intracellular mu and kappa chains, but express no membrane immunoglobulin. Immunoprecipitation of ¹⁴C-labeled amino acid or [³H]glucosamine-labeled P3HR-1 extracts with anti-mu serum brought down the same 61K mu chain. Anti-light-chain sera did not precipitate the truncated mu chain. P3HR-1 is a clonal derivative of the Burkitt lymphoma (BL) line Jijoye. The parental Jijoye line is membrane-IgM positive and contains two normal-sized mu chains. Both are precipitable by anti-mu and anti-kappa sera. In addition, anti-mu also precipitated a 61K mu chain. A 61K mu chain was also identified in the following somatic hybrids: PICATPO, an autohybrid of two different P3HR-1 sublines, PUTRAL and PUT/ARH-77, derived from the fusion of PUT with the membrane-IgG-positive BL line Rael and the lymphoblastoid cell line (LCL) ARH-77, respectively, and the HP-1 (PUT/HL-60) hybrid, derived from the fusion of PUT with the granulocytic leukemia line, HL-60. The 61K mu chain could not be detected in some other BL/BL hybrid combinations, namely RAMPUT (PUT/Ramos) and NAMPUT (PUT/Namalva). The anti-light-chain serum (lambda or kappa) had no detectable effect on the truncated 61K mu chain in any of the cases tested, suggesting a lack of assembly between the 61K mu chain and the light chain.