ENTPD1 and malaria: Subsets of malaria-specific CD8+ T cells co-express LAG-3 and PD-1 as well as other molecules associated with T cell exhaustion, for instance, T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) (18), T cell immunoreceptor with Ig and ITIM domains (TIGIT) (19), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) (20) and CD39 (21, 22).