Avian thymic hormone treatment of peripheral blood mononuclear cells from young chicks stimulates acute graft-versus-host reaction in chicken embryos.

Avian thymic hormone (ATH) is a parvalbumin produced by epithelial cells in the thymic cortex of chickens and circulates in the blood on a 5-day cycle. It stimulates precocious development of cell-mediated immunity. The effect of partially purified extracts of thymus (TE) and purified ATH were tested for their effect on the acute graft-versus-host reaction (GVHR). Treatment of chicks for their first 3-days of life did not enhance the acute GVHR produced by their PBMC in 14-day-old embryos. PBMC from 3-day-old chicks were treated in vitro with TE, ATH, thymosin fraction 5 or thymosin alpha1 for 2 h and injected into 14-day-old embryos. Bone marrow cells and thymic lymphocytes were treated with TE. Only PBMC treated with TE or ATH produced an enhanced acute GVHR. Because ATH targets gammadelta T cells, the data implicate participation of donor gammadelta T cells in the acute GVHR.