Interleukin (IL) 4, the cytokine that isn't there: reactivity of IL-4 antibodies with cells in IL-4 -/- mice

We analyzed cytokine expression in recipient spleens and cardiac allografts placed in mice that were unable to synthesize interleukin (IL)-4 due to disruption of the IL-4 gene (IL-4 -/-) and in wild-type (IL-4 +/+) mice. Polyclonal BL-4P and monoclonal 11B11, 1D11, and 24G2 anti-IL-4 antibodies were used to detect cell-surface and cytoplasmic antigens in sections of frozen tissue. All of the antibodies were found to react with non-IL-4 determinants associated with graft-infiltrating cells, and BL-4P, 1D11, and 24G2 bound to cells and connective tissue in the spleens of IL-4 -/- mice. The IL-4-producing cell line, X63Ag8-653 (X63), was used as a positive control for IL-4 staining and to test the ability of recombinant IL-4 to block the binding of antibodies to IL-4.