Isolation of an IL-13-dependent subclone of the B9 cell line useful for the estimation of human IL-13 bioactivity.

A novel sub-clone of the B9 hybridoma cell line (B9-1-3) has been selected by cloning following continuous culture in rhIL-13. This cell line shows an increased sensitivity to both hIL-13 and mIL-4 compared to the parental B9 cell line. The proliferative response to IL-13 can be blocked with an anti-IL-4 receptor monoclonal antibody but not with the soluble IL-4 receptor, suggesting that IL-13- and IL-4-binding receptor subunits are distinct but form part of a common receptor complex. Although the B9-1-3 cell line is still sensitive to picogrammes of IL-6, it can be used to measure IL-13 in the presence of IL-6 by inclusion of excess neutralizing IL-6 antibody. This cell line should thus prove useful both in measuring the IL-13 bioactivity and for the dissection of the molecular nature of the IL-13:IL-4 receptor complex.