Interleukin-5 increases the expression of alkaline phosphatase activity in murine B lymphocytes

Interleukin-5 (IL-5) was shown to enhance, in a dose-dependent fashion, the expression of alkaline phosphatase (APase) activity in splenic B cells stimulated with dextran sulphate (DXS). The potentiating effect of IL-5 was still more evident when assayed in large B cells than in small resting B cells, whereas IL-2, IL-4 and IL-6 were devoid of activity. Concomitant with increased APase expression, cell-cycle analysis by flow cytometry showed that large B cells in the early G1 phase were stimulated by IL-5, in conjunction with DXS, to enter G1B and to progress further through S and G2/M. A phosphorylation-dephosphorylation pathway could, thus, be involved in IL-5 transmembrane signalling.