In the adaptive immune response, do Helper T cells activate B cells and cytotoxic T lymphocytes to kill infected host cells? Do Helper T cells phagocytize bacteria and viruses?
T helper function
T helper is the cell which is activated by the macrophage. It has unique receptor called APC(antigen presenting cell). When the foreign antigen being eaten by the macrophage, some parts is being presented outside and then come the "naive-Th-cell" and undergo such signaling and maturation. This "naive-Th-cell" then being divided into 2 division, Th-1 mainly for cytotoxic T lymphocytes signaling to destroy the cell or the bacteria, and then Th-2 mainly for allergy reaction because the main signaling is for B-cell which is for antibody production.
T-helper cell does not do the phagoyctosis but important as mediator of other cell to do their job correctly as efficient killer machine.