Integrating the fact that MICA expression is upregulated in intestinal tissues of GVHD patients and that NKG2D is induced on CD8+ and CD56+ cells after HCT (see next section); it is likely that a mismatch between donor/recipient MICA molecules directly affects the strength of recognition/signaling and hence cytotoxicity by NKG2D bearing T/NK cells and/or the intestine-enriched Vδ1-bearing γδ T cells (both receptors able to recognize MICA directly). The gene discussed is CD8A; the disease is graft versus host disease.