Efficient immortalization of rheumatoid synovial tissue B-lymphocytes. A comparison between the techniques of electric field-induced and PEG fusion.

In this study, B-cells isolated from rheumatoid synovial tissue were immortalized, without prior in vitro stimulation, by means of electric-field induced fusion and conventional PEG fusion in order to compare the efficiency of these methods. Two myeloma cell lines were used as fusion partners, the murine myeloma Ag8 and the murine-human heteromyeloma HAB-1. The results of seven fusion experiments performed simultaneously with identical cell populations showed that fusion frequencies obtained by electrofusion were 4 to 35 times higher than by the PEG fusion technique. The morphological and immunohistochemical evaluation of synovial tissues used for fusion showed that only tissues exhibiting a follicular distribution of B-cells with a high percentage of CD 22-positive lymphocytes gave rise to high fusion yields and produced B-cell clones, whereas synovial tissues with the same percentage of plasma cells but lower percentages of CD 22 lymphocytes yielded very low fusion rates. In conclusion, electrofusion is more efficient for immortalizing small amounts of synovial tissue B-lymphocytes than PEG fusion, since high fusion frequencies could be obtained by this technique without the need for prior in vitro stimulation. Synovial tissue exhibiting a follicular distribution of B-lymphocytes with high percentages of CD 22-positive lymphocytes gave rise to high hybridoma yields and therefore an ideal source of human rheumatoid B-cell clones.