An investigation into the antigen-specificity of transfer factor in its stimulatory action on lymphocyte transformation.

Dialysable transfer factor (TF) was prepared from the buffy-coat cells of donors with known cell-mediated reactivity to tuberculin (PPD), streptococcal protein (SKSD) and diphtheria toxoid (DT). The effect of such preparations on the transformation by these antigens of lymphocytes from tuberculin-negative donors was investigated. Transformation was determined as incorporation of tritiated thymidine. The concentrations of SKSD and DT were adjusted for different lymphocyte donors so as to give, in the absence of TF, a low index of transformation (less than 10-fold) comparable to that obtained with PPD. TF from tuberculin-positive donors stimulated antigen-induced transformation by on average approximately 2-fold whereas TF from tuberculin-negative donors generally had little effect. This was so not for PPD as antigen but also for SKSD and DT, and sensitivity of TF donor to SKSD of DT was not a determining factor. TF also frequently increased background transformation in the absence of antigen. Although a small effect, this ability tended to reflect the activity of TF in the presence of antigen. It is concluded that neither the whole nor any significant part of this enhancement of transformation can be ascribed to an antigen-specific factor. Tuberculin-positive donors apparently yield a higher level of non-specific factor and possible reasons for this are discussed. The factor active in transformation may be responsbile for the TF phenomenon in vivo.