Do helper T cells ever destroy antigens on their own?
I know their main role is an intermediary.
I know their main role is an intermediary.
Do helper T cells ever destroy antigens on their own?
- Thread starter Gauss44
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No. Their function is to recognize and activate other immune cells.
(The caveat here is that I do not know everything about immunology, so there is possibly a scenario with exceptions. Through my experience studying for the MCAT, taking human physiology, microbiology, and immunology - I have not learned of a situation where Th cells directly act.)
The T cells that destroy pathogens are Cytotoxic T Cells and Natural Killer T Cells.
(The caveat here is that I do not know everything about immunology, so there is possibly a scenario with exceptions. Through my experience studying for the MCAT, taking human physiology, microbiology, and immunology - I have not learned of a situation where Th cells directly act.)
The T cells that destroy pathogens are Cytotoxic T Cells and Natural Killer T Cells.
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In response to your question: No. T helper cells have an indirect role, while Cytotoxic T cells differ in that they can either respond directly or function indirectly, by activating other responses. Here's a lot more detail if you care, but information you don't necessarily need to know for the MCAT:
It depends on what class of T Cell we are considering. T helper cells have an intermediary role; first naive CD4+ T cells recognize and bind to a foreign antigen processed by an APC (usually dendritic cell) and become activated. During this activation process, various cytokines trigger the production of a specific subset of T helper cells (ie. Th1, Th2, etc.), each with a unique role to a given immune response. For instance, Th1 are generally triggered in connection with viral infections. These cells have a unique role and release additional cytokines such as interferons, which prepare neighboring cells for a potential viral invasion. The neighboring cells respond accordingly to either kill themselves (if viral infected), or increase intracellular proteolytic acitivity of foreign molecules. Th2 is more geared towards parasitic infections and allergic reactions.
Additional insight: As you may already know, T helper cells have an important role in activating antibody production of B cells. Taking this a bit further, each subset of Th helps stimulate the production of a specific subclass of antibody (IgA, IgE, IgG) by interacting with antibody-producing plasma cells (activated colonies of naive B cells that are in the process of differentiating). For instance, IgE producing plasma cells are induced via specific Th2 cytokines called interleukins (IL for short). These IgE Ab's function particularly in response to allergic or parasitic infections, by first binding to mast cells and upon secondary exposure of the specific IgE antigen, cause the degranulation of mast cells which then triggers a massive inflammatory response.
CD8+ cells are also activated in a similar way (via APC), but these result in an army of Cytotoxic T cells. However, unlike T helper cells, these cells have both a direct and indirect role in mediating an immune response. By binding directly to a very specific foreign antigen (via cell-to-cell contact), they release perforins and granzymes which essentially destroy the infected cell via osmotic lysis. Cytotoxic T cells also have indirect roles via the release of interferons and other cytokines, which recruites other inflammatory cells such as NK cells to assist in targeting infected cells for them. And as mentioned earlier, the inferons themselves can help prepare neighboring cells to basically chill out and prepare their own defenses/kill themselves.
As a side note: It's also worth mentioning that Cytotoxic T cells function in response to viral infections or cancerous production (both which may stimulate the production of foreign antigens on the extracellular surface of infected cells). Therefore, high levels of Cytotoxic T cells most likely correspond to high levels of Th1 subclass due to their similar responses.
It depends on what class of T Cell we are considering. T helper cells have an intermediary role; first naive CD4+ T cells recognize and bind to a foreign antigen processed by an APC (usually dendritic cell) and become activated. During this activation process, various cytokines trigger the production of a specific subset of T helper cells (ie. Th1, Th2, etc.), each with a unique role to a given immune response. For instance, Th1 are generally triggered in connection with viral infections. These cells have a unique role and release additional cytokines such as interferons, which prepare neighboring cells for a potential viral invasion. The neighboring cells respond accordingly to either kill themselves (if viral infected), or increase intracellular proteolytic acitivity of foreign molecules. Th2 is more geared towards parasitic infections and allergic reactions.
Additional insight: As you may already know, T helper cells have an important role in activating antibody production of B cells. Taking this a bit further, each subset of Th helps stimulate the production of a specific subclass of antibody (IgA, IgE, IgG) by interacting with antibody-producing plasma cells (activated colonies of naive B cells that are in the process of differentiating). For instance, IgE producing plasma cells are induced via specific Th2 cytokines called interleukins (IL for short). These IgE Ab's function particularly in response to allergic or parasitic infections, by first binding to mast cells and upon secondary exposure of the specific IgE antigen, cause the degranulation of mast cells which then triggers a massive inflammatory response.
CD8+ cells are also activated in a similar way (via APC), but these result in an army of Cytotoxic T cells. However, unlike T helper cells, these cells have both a direct and indirect role in mediating an immune response. By binding directly to a very specific foreign antigen (via cell-to-cell contact), they release perforins and granzymes which essentially destroy the infected cell via osmotic lysis. Cytotoxic T cells also have indirect roles via the release of interferons and other cytokines, which recruites other inflammatory cells such as NK cells to assist in targeting infected cells for them. And as mentioned earlier, the inferons themselves can help prepare neighboring cells to basically chill out and prepare their own defenses/kill themselves.
As a side note: It's also worth mentioning that Cytotoxic T cells function in response to viral infections or cancerous production (both which may stimulate the production of foreign antigens on the extracellular surface of infected cells). Therefore, high levels of Cytotoxic T cells most likely correspond to high levels of Th1 subclass due to their similar responses.
