Effect of Dialysable Leucocyte Extracts from People of Known Tuberculin Sensitivity on the Migration of Normal Guinea-pig Macrophages in the Presence of Antigen

The hypothesis that transfer factor (TF) is an antibody-like molecule, possibly related to the T-cell receptor, has been explored. Experiments to test the hypothesis have involved determining whether TF can act as an antigen-dependent macrophage inhibition factor(MIF). Peritoneal exudate cells from normal guinea-pigs were migrated from capillary tubes in the presence and absence ofPPD and of 'dialys'able' TF prepared from the buffy-coat cells of people with strong positive or negative delayed reactivity to this antigen. At a low concentration ofPPD (8 pg/ml) there was a small but consistent inhibition ofmigration in the presence ofpositive, but not negative, TF. At a higher concentration (20 pg/ml) the situation was complicated by enhancing and inhibitory effects of PPD on migration occurring in the absence of TF. In half the experiments where PPD had little effect strong inhibition was seen in the presence of positive TF. Where PPD produced enhancement there was no further effect of TF; where PPD caused inhibition TF consistently overcame this, positive TF being more potent. These experiments cannot establish unequivocally an antibody-like structure for TF. Peritoneal exudates contain some lymphocytes and TF, whatever its nature, could be transferring sensitivity to these so that they produce MIF in the presence of antigen. Indeed, a correlation was observed between small effects of positive TF in the absence of PPD and the actions of PPD itself. There are difficulties in accepting that TF is a form of antigen, but this is an attractive solution from the standpoint ofmolecular weight.