There are five major types of CD4 T helper cells (Th). These include Th1, Th2, Th17, Treg (T regulatory), and Tfh (follicular T helper) cells. These subsets play crucial roles in orchestrating adaptive immune responses.
CD4 T helper cells are a critical component of the adaptive immune system. They don't directly kill infected cells, but rather coordinate the immune response by activating other immune cells, such as B cells (to produce antibodies) and cytotoxic T cells (to kill infected cells). This coordination is achieved through the secretion of cytokines, which are signaling molecules that influence the behavior of other immune cells.
The five major Th subsets are characterized by their distinct cytokine profiles and roles in immunity:
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Th1 cells: These cells primarily produce interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α). They are important for cell-mediated immunity against intracellular pathogens, such as viruses and bacteria. They also play a role in autoimmune diseases.
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Th2 cells: These cells produce interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-13 (IL-13). They are important for humoral immunity against extracellular parasites, such as helminths. They are also involved in allergic reactions.
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Th17 cells: These cells produce interleukin-17 (IL-17) and interleukin-22 (IL-22). They are important for immunity against extracellular bacteria and fungi, particularly at mucosal surfaces. They are also implicated in autoimmune diseases.
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Treg cells: These cells produce interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β). They suppress the activity of other immune cells, preventing autoimmunity and maintaining immune homeostasis.
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Tfh cells: These cells are located in the germinal centers of lymphoid organs and produce interleukin-21 (IL-21). They are essential for helping B cells produce high-affinity antibodies during an infection.
In summary, while all are classified as CD4 T helper cells, the five identified subsets (Th1, Th2, Th17, Treg, and Tfh) each possess distinct functions essential for proper immune responses.
