Solubilization of IgM-kappa specific surface material from Burkitt lymphoma cell lines.

Abstract

Two Burkitt lymphoma (BL)-derived cell lines, characterized by the accumulation of IgM-κ reactive material in their cell membrane, and one BL-line with no such reactivity were studied. Attempts were made to isolate and further characterize the reactive membrane material. Pepain digests of crude membrane preparations from the surface reactive cell lines were capable of blocking the direct membrane fluorescence reaction while the digest obtained from the non-reactive line demonstrated no blocking activity. Gel filtered and papain digested membrane material, from all three cell lines, produced similar elution curves when rechromatographed on a calibrated Sephadex G-150 column. The membrane fluorescence blocking activity of papain digests, derived from cells with μ and κ chain reactivity, appeared to be associated with material of a molecular weight less than 50,000. When this gel filtered material, and the corresponding fraction from the non-reactive cell line, were subjected to polyacrylamide gel electrophoresis a difference in electrophoretic mobility was noted. Electron microscopy revealed small protein fragments, some of linear dimensions compatible with a molecular weight of roughly 50,000 and the majority even smaller in all three preparations. μ and κ chain reactivity was demonstrable by indirect haemagglutination only in papain digested and gel filtered fractions from the two membrane reactive cell lines. Haemagglutation inhibition with Fc μ fragments indicated that these fragments inhibited the anti-IgM reactivity of red cells coated with the proteolytic products of the two membrane reactive cell lines.