A new human fusion partner, HK-128, for making human-human hybridomas producing monoclonal IgG antibodies.

A hypoxanthine-aminopterin-thymidine (HAT) sensitive human fusion partner cell line, HK-128 was established from a human plasmacytoma line, LICR-LON-HMy2 (HMy2). The HK-128 cells showed a 100% cloning efficiency. Fusion efficiency of HK-128 was so high that one hybridoma cell was produced by fusion of 10(5) cells of HK-128 with lymphocytes, obtained from lymph nodes of breast cancer patients. About 90% of the resulted hybridomas were IgG producers. The remainder revealed IgM producing activity, which was lost by long term culture. This result indicates that the HK-128 cell line has an advantage for making hybridoma cells producing IgG. Among ca. 7,000 hybridomas obtained by fusion of HK-128 with lymphocytes of a breast cancer patient, we could establish a hybridoma cell line which produced IgG specifically reacting to a human breast cancer cell line, MCF-7.