In general, co-infections showed little effect on net TB-antigen stimulated cytokine responses, except for increased IL-21 production in HHCs with helminths compared to those without helminths (geometric mean 6.07 vs 2.45 pg/ml, respectively, p = 0.05), decreased TNFα levels in malaria versus no malaria (geometric mean 1.83 vs 4.36 pg/ml, respectively, p = 0.05), and reduced TNFα production in HIV versus no HIV co-infection (geometric mean 1.00 vs 4.04 pg/ml, respectively, p = 0.01)(figures 3a, 3b, 3c). The gene discussed is IL21; the disease is malaria.