Suppressive effect of interferon‐γ on the BCL₁ cell‐dependent interleukin 5 bioassay

Proliferation of BCL1 cells, generally used for the measurement of murine interleukin (IL)5, is shown to be strongly suppressed by interferon (IFN)-gamma. This effect can be abrogated by the addition of anti-IFN-gamma antibodies. Thus, the IL5 activity of culture supernatants derived from T cells simultaneously producing IFN-gamma and IL5, can only be seen with BCL1 cells in the presence of anti-IFN-gamma antibodies. If anti-IFN-gamma antibodies are omitted, T cells which produce both, IFN-gamma and IL5, may mistakenly be grouped into the TH1 subtype producing only IFN-gamma, but no IL5.