Induction of hair regrowth in the alopecia site of IFN-gamma knockout mice by allografting and IFN-gamma injection into the transplantation site.

We previously demonstrated that around 6 weeks of age most of the interferon-gamma (IFN-gamma)(-/-) but none of the IFN-gamma(+/+) C57BL/6 mice began to lose hair in their dorsal or occipital areas or both and that a single s.c. injection of IFN-gamma into IFN-gamma(-/-) mice at 3 but not at 8 weeks of age (or later) could protect all the mice from alopecia. Here, we report hair regrowth in the alopecia site of IFN-gamma(-/-) mice at 8 weeks of age (or later) by the combination of IFN-gamma and allografting. Skin or tumor allografting and IFN-gamma injections into the transplantation site induced hair regrowth in the alopecia site of IFN-gamma(-/-) mice at 8-66 weeks of age, whereas IFN-gamma injections into the hairless site or allografting alone was ineffective in causing the hair regrowth. Histologic findings showed that the hair cycle in the region of alopecia of IFN-gamma(-/-) mice was blocked at the anagen stage and that in the IFN-gamma(-/-) mice treated with IFN-gamma and allografting, the cycle was at the telogen stage. The therapeutic effects were maintained for >1 year.