Human transfer factor: Structural properties suggested by HPRP chromatography and enzymatic sensitivities

Leukocyte extracts containing human transfer factor (TF) were fractionated by exclusion chromatography, and the active fraction (Sephadex G25, Fraction IIIa) was subjected to high pressure, reverse phase (HPRP) chromatography and enzymatic degradation. TF activity was assessed by the systemic transfer of dermal skin test reactivity from KLH-immunized donors to naive recipients. Preparative HPRP chromatography resolved Fraction IIIa into multiple chromophoric regions, 2 of which demonstrated transfer of KLH reactivity. Alkaline phosphatase treatment of Fraction IIIa converted the major ultraviolet-absorbing component, 5'-inosine monophosphate, to inosine and resulted in TF activity being restricted to 1 region. This HPRP region (RIA) contained less than 1% of the UV₂₅₄ active material in Fraction IIIa but greater than 90% of the reactivity. The sensitivity of TF to pronase, proteinase K, phosphodiesterase I, and phosphodiesterase II was evaluated by inhibition of systemic transfer of KLH reactivity. Pronase and proteinase K destroyed systemic transfer activity and the pronase destruction could be inhibited with traysylol. Phosphodiesterase I, a 3' exonuclease, destroyed activity, whereas phosphodiesterase II, a 5' exonuclease, did not. The data are consistent with a phosphodiester-containing polypeptide in the structure of human TF for KLH reactivity.