Augmentation of Proliferation of Human Mixed Lymphocyte Culture by Human α-Fetoprotein

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Abstract
We have studied the effects of purified human α1-fetoprotein (AFP) of hepatoma origin on the kinetics of one-way lymphocyte proliferation in a mixed human lymphocyte culture system. Human serum albumin was employed in parallel control studies. Although AFP, over a wide range of concentrations from 5 ng/ml to 2 mg/ml, had no mitogenic activity on a single lymphocyte population, significant augmentation of the proliferative response was seen at the three different times of harvesting in the system of one-way allogeneic stimulation. When the addition of the AFP to this system was delayed to 24 hr after culture initiation, the AFP was still effective in producing augmented proliferation. However, no effect on the normal mixed lymphocyte reaction was seen upon addition of the AFP at either 48 or 72 hr after initiation of the cultures. In completely parallel control studies, human serum albumin used at the same concentrations as the AFP produced no modifications of the normal mixed lymphocyte culture response when compared to control cultures incubated in media without added serum proteins. Thus, the preparation of highly purified human AFP studied had no immunosuppressive activity, but actually showed a stimulatory activity on mixed lymphocyte proliferation when employed at relatively high concentrations.