PTPRC and graft versus host disease: Analysis of immune reconstitution shows a marked decrease in B220+ B cells in allogeneic HSCT recipients of 2.5 x 106 T cells (Figure 1E), a surrogate of GVHD in other murine allogeneic HSCT models (32, 33), as well as marked decreases in NK cells (Figure 1F) and CD8+ T cells (Figure 1G), the cells that would typically respond to IC bound to tumor (16, 25).