# Helper T-Cells **Helper T-Cells** (or CD4 T-Cells) are a special class of T-Cells that don't directly combat bacterial cells, instead opting to boost the performance of other [[Cells of the Immune System|immune cells]]. The key difference between Helper and [[Killer T-Cells]] is which co-receptor they have ## Helper T-Cell Diversity ![[Helper T-Cell Diversity.png]] ### $T_{h}1$ Cells The TH1 subset of helper T cells activates macrophages to increase phagocytosis and to kill those phagocytosed pathogens that are resistant to phagocytic killing. ### $T_{h}2$ Cells The TH2 subset of helper T cells responds to parasite infections by secreting cytokines that activate mast cells, basophils, and eosinophils. The mediators released by these cells induce contractions of smooth muscle that eject parasitic worms and protozoans from the gut and respiratory tracts. ### $T_{h}17$ Cells TH17 cells—activate neutrophils to phagocytose and eliminate extracellular bacteria - Regulatory T Cells ($T_{reg}$) ### $T_{fh}$ Cells (Follicular Helper T-Cells) Follicular Helper T-Cells will remain within the [[Lymph Nodes|lymph node]] after activation ### $T_{reg}$ Cells (Regulatory T-Cells) ## Changes After Activation ![[Helper T-Cell Receptors After Activation.png|500]] ]]