TH cells secrete cytokines for only a short period after they have been activated; the range of cytokines that T<sub>H</sub> cells secrete after activation chiefly determines their function. Different T-helper cell subpopulations (T<sub>H</sub>1, T<sub>H</sub>2 and T<sub>H</sub>17 cells) secrete different sets of cytokines. | TH cells secrete cytokines for only a short period after they have been activated; the range of cytokines that T<sub>H</sub> cells secrete after activation chiefly determines their function. Different T-helper cell subpopulations (T<sub>H</sub>1, T<sub>H</sub>2 and T<sub>H</sub>17 cells) secrete different sets of cytokines. |