Nonencephalitogenic CD4^-CD8^- Vα2Vβ8.2⁺ anti-myelin basic protein rat T lymphocytes inhibit disease induction

Recently there has been a number of reports suggesting that CD4^-CD8^- T cells participate in the processes of inflammatory reaction. In an attempt to delineate the distinctive functions of double negative (DN) T lymphocytes in an autoimmune-induced disease, we isolated and cloned such T cells, along with control CD4⁺ cells, from Lewis rats immunized with guinea-pig myelin basic protein in CFA. Both clones proliferated in response to the guinea-pig myelin basic protein and its synthetic encephalitogenic peptide, and expressed the same TCR V genes homologous to the mouse Vα2 and Vβ8.2 families that appear to be the defining entity of experimental autoimmune encephalomyelitis (EAE). Moreover, the TCR D and J region gene products of the DN cell were found to be similar to another encephalitogenic rat T cell clone. The two T clones did not differ markedly in their ability to produce TNF and IL-2 and to adhere to vascular wall-derived extracellular matrix- and laminin-coated plates. Surprising, therefore, was the finding that, although the CD4⁺ T lymphocytes were capable of inducing EAE, the DN cells did not elicit disease but rather inhibited subsequent EAE induction. Thus, TCR Vα2V/β8.2 and its junctional region gene products are not the only prerequisite segment for a T cell to become encephalitogenic. We suggest that the important determinants of the T cell ability to induce disease are features of the T cell, other than or in addition to, the T cell receptor.