TIGIT and infection: At peak viremia the frequencies of MAIT cells expressing HLA-DR, CD38, Programmed Death 1 (PD-1), T cell immunoreceptor with Ig and ITIM domains (TIGIT) and granzyme B (GrzB) were elevated above pre-infection frequencies, and transcripts for these proteins remained elevated above pre-infection expression throughout acute HIV-1 infection (Fig. 2a and Fig. 2b).