The S-specific CD8+ T cells, targeting S436 or S525 domains, had an effector memory phenotype (CD45RA+ CCR7- CD62L-) (115, 128) Interestingly, CTL responses could be elicited in a small minority of healthy patients without any history of SARS-CoV infection (129), which suggests that there may be cross-reactive memory T cells naturally present in the T cell repertoire that can elicit recall-like responses following SARS-CoV infection. This evidence concerns the gene SELL and severe acute respiratory syndrome.