Interleukin-4 induces apoptosis in cultured human follicular keratinocytes, but not in dermal papilla cells.

The importance of apoptosis in hair follicle cycling is still not clearly understood, however, its regulation in follicular keratinocytes (FK) during bulb regression (catagen) may be essential for hair regrowth. So far, the control of FK apoptosis remains unknown. In this study, the anti-inflammatory cytokine IL-4 was found to induce apoptosis dose and time dependently in cultured human FK, in contrast to other agents known to inhibit hair growth such as IL-1alpha, IL-1beta, TNFalpha and TGFbeta, as shown by DNA fragmentation.