Although the role played by 4-1BB in vivo during MTB infection needs further investigations, this receptor could be effectively involved in the immunological responses against mycobacterial infection since expression of CD137, the human counterpart of 4-1BB, was found on a sub-population of the T-lymphocytes infiltrating lung tuberculous granulomas in patients with TB [63]. The gene discussed is TNFRSF9; the disease is tuberculosis.