HCAR1 and infection: • No direct studies investigating GPR81 expression or signaling during Mtb infection• Mtb relies on host fatty acids during infection (Singh et al., 2012; Lee et al., 2013)• PD-1 deficiency or blockade can increase TB susceptibility and severity (Lázár-Molnár et al., 2010; Tousif et al., 2011; Barber et al., 2019)