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 (Fc epsilon RII)-CD23 expression on B cells as well as on other human mononuclear cells. We demonstrate here that, in opposition with previous reports, recombinant IL2 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 IL2. Similarly, upon triggering with anti-mu and IL2, normal tonsillar B lymphocytes also demonstrate an increase of CD23 expression but this was observed only on day 3. Interferon-gamma was able to inhibit this IL2-mediated up-regulation of CD23 on normal B cells but not on CLL-B cells; on those cells interferon-gamma was similarly unable to inhibit the IL4-mediated CD23 up-regulation. These results suggest that CD23 regulation is complex and related to the stage of activation and the cell type.