Isotype-directed enrichment of B cells by magnetic beads in the generation of immunoreactive human monoclonal antibodies.

Pooled lymphocytes collected from cancer patients were mixed with a biotinylated murine MAb specific to human IgG4. To this were added streptavidin-conjugated magnetic beads. After magnetically separating the bead-lymphocyte complex, the B cells were washed and fused with the WIL-2 derived human fusion partner, SHFP-1. Subsequently derived human-human hybridomas were screened for IgG4 immunoreactivity to target tumor cell lines. Several hybridomas reacted with a variety of malignant cell types, including melanoma, neuroblastoma, and pancreatic tumor cells. One hybridoma in particular, designated SC-GM4, recognized an antigen by Western blot with an apparent molecular weight of 57 kDa. This facile approach of magnetically separating selected populations of lymphocytes should be relatively simple to apply to other antigens and antibodies to preselect the type, class, and properties of the desired MAb.