FIGURE 1.

Dual TCR T cells are increased among alloreactive T cells. CFSE-labeled T cells from B6 (H-2^b) mice cultured in MLR with irradiated splenocytes from either CBA (H-2^k) or BALB/c (H-2^d) mice or anti-CD3 and anti-CD28 mAbs for 4 d were analyzed by flow cytometry for the presence of dual TCR T cells. Cells were gated on CD4⁺ and CD8⁺ T cells, and alloreactive T cells were distinguished by gating on cells with diluted CFSE. A, Dual TCR T cells were consistently observed in higher frequency among T cells that had divided in response to allogeneic stimulation as compared to undivided controls. FACS data of dual TCRα T cells from a representative experiment with allogeneic stimulation by B6.K splenocytes show the increased dual TCRα T cells among T cells that had divided in response to allogeneic stimulation as measured by CFSE dilution. B, To compare the frequency of T cells expressing dual TCRα between populations and 5 independent experiments, T cell numbers were normalized to Vα2⁺ cells, demonstrating a consistent and significant (mean ± s.d. * p < 0.05 ** p < 0.01) increase in dual TCR T cells among alloreactive T cells. C, Increased dual TCR T cells were also consistently and significantly (mean ± s.d. * p < 0.05 ** p < 0.01) observed among alloreactive CD4⁺Vα2⁺ T cells. Stimulation with anti-CD3 and anti-CD28 mAbs did not result in significantly increased dual TCRα T cells (p = 0.18–0.10).