Establishment of a bromelain-treated isologous red blood cell reactive B cell clone by somatic hybridization.

Splenic B cells of BALBc mice were fused with 2.52M, a mutant of a B cell line, in the presence of polyethylene glycol and dimethyl sulfoxide. AT73.14, a subclone of a resulting hybridoma, expresses B cell surface antigens on the cell membrane, namely IAd, IgM, B220, and receptors for C3 fragment of complement (C3R), the Fc portion of IgG (FcγR), and interleukin 2 (IL-2R). It also possesses a receptor molecule for mouse red blood cells treated with bromelain (Br-MRBC) on its surface, by rosette-forming assay with Br-MRBC. In contrast, parental 2.52M does not express IAd on the cell membrane and does not bind to Br-MRBC on the same conditions. Thus, it is likely that AT73.14 may be an autoreactive B cell clone specific for Br-MRBC. Interestingly, AT73.14 could generate a significant number of IgM-secreting cells when treated with Br-MRBC; this was followed by a marked decrease in the expression of B cell surface markers on the cell membrane. In addition, this differentiative response of the cells greatly augmented in the presence of B151-TRF, a B cell differentiation factor, although B151-TRF alone showed only a marginal effect on the generation of IgM-secreting cells. The result suggests that this kind of an autoreactive B cell clone may provide a good model for the study on the mechanism of autoimmune responses.