TNF and brucellosis: As shown in Table 3, no significant associations were found between serum levels of IL-13, TNF-α and IL-12 and gene polymorphisms [TNF-α (− 238 G/A), IL-12 (+ 1188 A/C), IL-13 (− 1112C/T) and IL-13 (−1512A/C)] in patients with brucellosis and controls.