T-CELL RECEPTOR ALPHA-CHAIN DEFINES THE ANTIGEN-SPECIFICITY OF ANTIGEN-SPECIFIC SUPPRESSOR FACTOR BUT DOES NOT IMPART GENETIC RESTRICTION

Previous studies utilizing NP (4-hydroxy, 3-nitrophenyl acetyl hapten) -specific, T suppressor hybridomas have indicated that expression of T CR-alpha, but not TCR-beta, mRNA is required for expression of Ag-spec ific suppressor factor bioactivity. Suppressor-effector factor has bee n shown to be Ag specific and I-J restricted. Although the expression of TCR-alpha mRNA was necessary for suppressor activity, the role of T CR-alpha, as it pertained to the functional properties of T cell suppr essor factor (TsF), was not established. To determine which properties of TsF could be accounted for by TCR-alpha expression, TCR-alpha cDNA , derived from NP-specific, suppressor T cell (Ts) hybridomas, was tra nsfected into recipient Ts hybridomas of a second Ag specificity. The resulting heterologous transfectants displayed NP-specific, geneticall y restricted TsF activity. The Ag specificity corresponded to that of the TCR-alpha donor; however, the genetic restriction was influenced b y the recipient cell, implying that TCR-alpha did not control genetic restriction of the TsF. Examination of TCR-beta expression in one of t he MHC-restricted transfectants indicated that the genetic restriction of TsF could not be accounted for by TCR-beta gene products. The data support the conclusion that TCR-alpha expression is not only obligate for TsF bioactivity, but that the Ag specificity of the TCR-alpha dic tates the Ag specificity of the resulting suppressor factor.