FIGURE 4.

Dual TCR T cells are profoundly increased among T cells mediating GvHD. B6 Ly5.1⁺ bone marrow cells and splenocytes were transferred into lethally irradiated (B6 × CBA)F₁ or control irradiated B6 mice. Lymphocytes were collected from spleens and lymph nodes and analyzed by flow cytometry using the 4 available Vα mAbs. A, Mice with GvHD demonstrated dramatically increased numbers of dual TCR T cells by FACS analysis compared to control B6 mice. FACS analysis of representative mice illustrate markedly increased dual TCR T cell frequency in mice with GvHD. Dual TCR T cells from mice with GvHD also exhibited down-regulation of their TCR, consistent with T cell activation. B, Dual TCR T cells from mice with GvHD are larger as measured by forward scatter, consistent with activation. C, Normalization of Vα2⁺ T cells expressing a second TCRα quantifies the dramatic increase in dual TCR T cells in mice with GvHD. Significantly more Vα2⁺ T cells from mice with GvHD expressed a second TCRα (mean ± s.d * p < 0.05 ** p < 0.01). D, The increase in dual TCR T cells was also observed among both alloreactive CD4⁺Vα2⁺ T cells and E, CD8⁺Vα2⁺ T cells.