Isolation of tumor-derived immunoglobulin-idiotype from peripheral blood mononuclear cells in a B-cell lymphoma patient with minimal disease.

Active immunization with autologous idiotypic immunoglobulin, obtained by somatic fusion techniques, has been shown to be a useful alternative treatment in patients with B-cell lymphoma. Nevertheless, the requirement for biopsy specimens to obtain lymphoma cells could be a limitation to this therapeutic strategy. We address the question of whether peripheral blood samples containing small amounts of tumor cells can be used as appropriate fusion partners to rescue tumor-derived idiotypic proteins. In this report, we show that hybrid cells can be obtained from somatic fusions of K6H6/B5 heterohybridoma with lymphoma cells obtained from both lymph node (LN) and peripheral blood mononuclear cells (PBMC) containing only minor amounts of tumor cells. Some hybrid cells obtained from LN or PBMC fusions present an immunoglobulin (Ig) heavy-chain gene rearrangement identical with that of the original tumor and secrete identical Ig protein containing the expected H and L chains.