Infection of sh2d1a-deficient mice with lymphocytic choriomeningitis virus (LCMV), Toxoplasma gondii, or murine gammaherpesvirus-68 recapitulates many of the disease phenotypes observed in EBV-infected XLP patients, including hyperproliferation of CD8 T cells (Czar et al., 2001; Wu et al., 2001; Yin et al., 2003; Chen et al., 2005) and fatal immunopathology (Crotty et al., 2006). Here, CD8A is linked to infection.