[Lymphocyte macrophage activation factor. Comparison of the mode of production in man and mice].

A macrophage activating factor (MAF) has been previously described in mixed lymphocyte cultures (MLC) between the donor and the recipient of a mouse skin allograft. This factor can render macrophages cytotoxic against mouse mastocytoma targert cells. The present work demonstrates the production of a similar factor in the human, using macrophages from uremic patients treated with peritoneal dialysis. There is, however, an apparent difference between mouse and human MAF. In the mouse the production of MAF in primary MLC is inconsistent, late and weak, while it is regularly found in large amounts in MLC between a donor and a recipient of a skin allograft. Conversely, in the human, MAF is consistently found in primary MLC as well as in MLC between two individuals previously sensitized to each other by a skin allograft followed by repeated white blood cell injections.