Biological characterization and partial purification of an idiotype and antigen specific T cell lymphokine

An idiotype (Id) and antigen-specific T cell lymphokine has been partially purified and characterized biologically. This lymphokine appears to be derived from the T helper2 (Th2) lymphocyte and plays a key role in the optimal expression of the cross-reactive idiotype (CRI+-TMA) associated with both anti-phenyltrimethylammonium (TMA) and anti-trinitrophenyl (TNP) antibodies. An apparent molecular weight of 30-35 Kd was determined using molecular sieve chromatography. Upon SDS-polyacrylamide gel electrophoresis (SDS-PAGE) however, the biological activity migrated to 68 Kd as well as 35 Kd. Equivalent amounts of activity are found in both SDS-PAGE fractions. The Th2F has two isoelectric points, 5.7 and 6.3, although 99% of the activity is found at pH 6.3. The Id-enhancing factor is an acid stable and heat labile protein. As in the case for the expression of serum CRI-TMA, the production of the Th2F is linked to the allotype (Igh-1/sup e/) of the heavy chain locus. Using Con A Sns from various genetically distinct strains of mice, it has been shown that the production of the Th2F is allotype-linked, and works across major histocompatibility (MHC) barriers. Isolation of Th2F has been carried out using a combination of affinity chromatography and gel filtration. The partially purified material has been 125I labeled and analyzed by SDS-PAGE and flat bed isoelectric focusing. Two radiolabeled proteins which could be the Th2F were identified