Low molecular weight B cell growth factor-responsive cloned human B cell lines. I. Phenotypic differences and lack of requirement for CD23 (Fc epsilon RII).

The EBV-transformed B cell line JR-2 proliferates in response to partially purified preparations of low m.w. B cell growth factor (LMW-BCGF). Two clones of JR-2 were generated that retained this LMW-BCGF responsiveness, exhibiting similar dose/response characteristics but differing phenotypically. The B10 clone grows as single, discrete, small round cells, whereas D3 grows in aggregates. The clones also differ in the expression of cell surface Ag, D3 being weakly DR+ and strongly CD23+, whereas B10 lacks these Ag. The CD23 on D3 cells binds IgE. Both clones are T9+, 4F2+, B1-, B2- and CALLA-. D3 expresses surface IgG and differentiates in the presence of LMW-BCGF, to secrete IgG. B10 lacks surface and cytoplasmic Ig and fails to differentiate in response to LMW-BCGF. CD23 cannot be induced on B10 by incubation with either LMW-BCGF or IL-4. B10 does not shed CD23 and shed CD23 is not a growth factor for either cloned line. Expression of CD23 on D3 cells is not affected by preincubation with LMW-BCGF. Neither B10 or D3 cells respond to rIL-1, rIL-2, rIL-4, rIL-6, rTNF-alpha/beta, rIFN-gamma, or to high m.w. BCGF (Namalwa), alone or in combination. Both clones absorb BCGF activity and crossover absorptions indicate that the clones remove growth factors required by each other. D3 and B10 both appear therefore to respond selectively to LMW-BCGF. These data suggest that the loss of CD23 from a cloned derivative of the cell line JR-2, although accompanied by considerable phenotypic change, is not associated with the disappearance of LMW-BCGF responsiveness, indicating that CD23 is not the essential receptor for LMW-BCGF.