Leukotactic factor elaborated by mixtures of genetically dissimilar cells.

Mixtures of immunologically competent cells, from genetically dissimilar donors from inbred strains of mice, rats, or Syrian hamsters, cultivated in vitro elaborate into the medium a factor capable of attracting polymorphonuclear cells when it is injected into the skin of irradiated hamsters. Supernatant medium of cultured node cells from genetically identical donors contains no leukotactic activity. The degree of the cell accumulation seemed to parallel closely the degree of histoincompatibility.