1. Recognizing and Destroying Infected Cells:
* T cells, specifically cytotoxic T cells (CTLs), are responsible for identifying and destroying cells infected with viruses, bacteria, or parasites. They achieve this by recognizing specific antigens presented on the surface of infected cells.
* This process involves MHC (Major Histocompatibility Complex) molecules, which present antigen fragments to T cells.
* Upon recognition, CTLs release cytotoxic substances like granzyme and perforin, which induce apoptosis (programmed cell death) in the infected cell.
2. Orchestrating Immune Responses:
* Helper T cells (Th cells) act as the "commanders" of the immune system.
* They recognize antigens presented by antigen-presenting cells (APCs), such as macrophages and dendritic cells.
* Based on the type of antigen, Th cells differentiate into different subtypes (Th1, Th2, Th17) that activate specific immune responses, like:
* Th1 cells help activate macrophages and cytotoxic T cells, effective against intracellular pathogens.
* Th2 cells stimulate antibody production by B cells, crucial for fighting extracellular pathogens.
* Th17 cells play a role in inflammatory responses against extracellular pathogens and fungi.
3. Memory and Immune Tolerance:
* Memory T cells are generated after exposure to a specific pathogen.
* They "remember" the antigen and quickly activate the immune response upon re-encountering the same pathogen, providing long-lasting immunity.
* Regulatory T cells (Tregs) play a vital role in maintaining immune tolerance, preventing immune responses against self-antigens and minimizing autoimmune reactions.
In summary, T cells are highly specialized cells that:
* Identify and eliminate infected cells
* Orchestrate immune responses
* Establish immune memory
* Maintain immune tolerance
These functions are essential for protecting the body from a wide range of infections and diseases.
