◾ BTLA expression increases in patients with COVID-19 (90), Mtb (91), CMV (92), and HBV (93) infection.◾ BTLA-/- mice are more resistant to helminth (96), MHV-3 (97), Plasmodium yoelii strain 17NL (98), and listeriosis infection (99). The gene discussed is BTLA; the disease is COVID-19.