T cell receptors in an IL-10-secreting amino acid copolymer-specific regulatory T cell line that mediates bystander immunosuppression.

The T cell receptors from the regulatory IL-10-secreting T cell line induced by the random amino acid copolymers poly(F,Y,A,K,)n in SJL mice (H-2(s)) have been characterized, cloned, sequenced and expressed both in 293T cells and in 2 different TCR alpha(-)/beta(-) T cell hybridomas. The usage of TCR alpha and beta V regions in the cell line was oligoclonal. Four TCR alpha/beta pairs cloned from single cells of the T cell line were inserted into a retrovirus vector linked by an oligonucleotide encoding the 2A peptide that spontaneously cleaves in vivo. After cotransfection of this vector with a CD3 vector into the 293T cells, the TCR were surface expressed. Moreover, after transduction into the 2 T cell hybridomas, all 4 were functional as evidenced by their response to stimulation by poly(F,Y,A,K)n. All 4 pairs were Valpha3.2(3.5)/Vbeta14, a prominent clonotype found in the poly(F,Y,A,K)n-specific T cell line. These V regions are identical to those recently found in a regulatory T cell line that secretes both IL-4 and IL-10 induced in B10.PL mice with a different MHC hapotype (H-2(u)) by a small peptide obtained from an autoimmune TCR of that strain. These data lead to a hypothesis regarding the origin of the epigenetic modifications that lead to selective cytokine secretion in T cells.