The probability of progression from latent infection to active clinical tuberculosis is determined by bacterial, host, and environmental factors, including: the initial bacillary load, related to the severity of the disease in an index case and the proximity of contact; suppression of cellular immunity induced by the human immunodeficiency virus (HIV); tumor necrosis factor α (TNF-α) inhibitors; glucocorticoids; and organ transplantation [6]. The gene discussed is TNF; the disease is tuberculosis.