Given the clinical and experimental evidence showing a crucial role of the IFN-γ pathway in host defence against TB, we investigated eight candidate genes which could potentially modulate the function of this vital cytokine, namely interleukin 4 (IL4), interleukin 10 (IL10), interleukin 12B (IL12B), interleukin 12 receptor beta 1 (IL12RB1), interleukin 12 receptor beta 2 (IL12RB2), interleukin 18 (IL18), wingless-type MMTV integration site family, member 5A (WNT5A) and frizzled homolog 5 (FZD5). The gene discussed is IL18; the disease is tuberculosis.