Regulation by interleukin 2 of CD23 expression of leukemic and normal B cells: comparison with interleukin 4

Recombinant interleukin (IL) 4 has been shown to be able to up‐regulate low‐affinity Fc receptor for IgE (FcεRII)‐CD23 expression on B cells as well as on other human mononuclear cells. We demonstrate here that, in opposition with previous reports, recombinant IL 2 also can up‐regulate CD23 expression on B cells. This was first observed on CLL cells which represent a monoclonal proliferation of B cells arrested at an intermediate stage of activation. Cells of 5 out of 12 B‐CLL studied display such an increase and all 5 proliferated, in vitro, directly in response to IL 2. Similarly, upon triggering with anti‐μ and IL 2, normal tonsillar B lymphocytes also demonstrate an increase of CD23 expression but this was observed only on day 3. Interferon‐γ was able to inhibit this IL 2‐mediated up‐regulation of CD23 on normal B cells but not on CLL‐B cells; on those cells interferon‐γ was similarly unable to inhibit the IL 4‐mediated CD23 up‐regulation. These results suggest that CD23 regulation is complex and related to the stage of activation and the cell type.