There are several functions of cell mediated immunity. One function involves T cells identifying and destroying cells infected with intracellular pathogens, including viruses and certain bacteria. T helper cells, which play a central role in coordinating immune responses. In specific, TH1 cells activate macrophages to neutralize recently ingested pathogens. TH2 cells initiate the humoral response by activating B cells to produce various antibody types, including those with weaker opsonizing properties. Regulatory T cells (Tregs) modulate immune responses through preventing excessive inflammation and autoimmunity. They help maintain immune tolerance by suppressing the activity of other T cells. Memory T cells develop after an initial encounter with a pathogen. They persist long-term and initiate a rapid and strong immune response upon re-exposure to the same pathogen, providing immunological memory.