Loss of original antigenic specificity in T cell hybridomas transduced with a chimeric receptor containing single-chain Fv of an anti-collagen antibody and Fc epsilonRI-signaling gamma subunit.

摘要

T cell hybridomas HCQ6 and MD.45 acquired Ab-type specificity to collagen type II, when engrafted with a chimeric cell surface receptor, scC2Fv/gamma, which includes the single-chain Fv domain (scFv) of the anti-collagen type II mAb C2 and the signaling gamma subunit of the Fc epsilonRI. When transduced into MD.45 cells, scC2Fv/gamma or its mutated form lacking immunoreceptor tyrosine-based activation motif (ITAM), scC2Fv/gammaIC-, formed mainly homodimers. A small proportion of these molecules formed heterodimers with endogenous CD3zeta in these hybridoma cells. By contrast, in HCQ6 cells, the majority of scC2Fv/gamma and scC2Fv/gammaIC- molecules formed heterodimers with CD3zeta, and only a small proportion of them was expressed as homodimers. Stimulation with plastic-immobilized collagen induced IL-2 production in scC2Fv/gamma-transduced MD.45 cells, but not in MD.45 cells transduced with the ITAM-less chimera scC2Fv/gammaIC-. HCQ6 cells transduced with scC2Fv/gamma responded to plastic-bound collagen. Due to the high content of CD3zeta-associated chimeras, HCQ6 cells transduced with the ITAM-less scC2Fv/gammaIC- chimera were also responsive to plastic-bound collagen. When cells were stimulated with collagen in solution, MD.45 cells transduced with scC2Fv/gamma produced IL-2, whereas transduced HCQ6 cells were unresponsive, hence suggesting that the ability of cells transduced with scC2Fv chimeras to respond to soluble collagen correlated with predominant expression of divalent scC2Fv/gamma homodimers, but not monovalent scC2Fv/gamma-CD3zeta or scC2Fv/gammaIC(-)-CD3zeta heterodimers. Of interest, expression of CD3 subunits in hybridomas transduced with scC2Fv chimeras was reduced, resulting in decreased response to cognate Ags.