However, earlier studies indicated that human CD4+ and CD8+ T cells proliferate in response to NSG mouse spleens and that this in vitro response and the development of GVHD in vivo involves the presence of MHC class II β chain and MHC class I β2 microglobulin chain, respectively [73,95], supporting a role for host murine APCs in the activation of donor human T cells. The gene discussed is CD4; the disease is graft versus host disease.