The Journal of Immunology, Vol 145, Issue 10 3177-3180, Copyright © 1990 by American Association of Immunologists

ARTICLES

Hybridomas derived from lipopolysaccharide-activated anti-mu-treated B cells have active suppression of IgM secretion, demonstrable by secondary fusion

AR Lawton, VS Summerlin and JS Dooley
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232.

Treatment of LPS-stimulated mouse B cells with bivalent anti-mu antibodies suppresses differentiation to Ig-secreting cells without interfering with proliferation. This treatment selectively inhibits up- regulation of transcription of differentiation-related genes. Induction of anti-mu suppression requires RNA and protein synthesis, suggesting involvement of a transcriptional repressor. We describe experiments designed to capture the repressed phenotype of anti-mu-treated cells. Fusions of anti-mu-treated cells with the B lymphoma line M12.4.5, but not plasmacytoma Ag8.653, yielded a significantly lower frequency of secretory hybridomas than did parallel fusion of cells treated with LPS only. To test for active repression, nonsecreting cloned hybridomas were secondarily fused to LPS-activated normal B cells. Secondary hybridomas with anti-mu parentage had a very low frequency of IgM secretion. Active suppression could only be demonstrated by secondary fusion. Neither supernatants nor extracts of repressor hybridomas influenced LPS-driven differentiation of normal B cells. These results confirm that this form of differentiation suppression is an active process, probably mediated by transcriptional controls. Repressor hybridomas should prove useful for studies of molecular mechanisms.