Describe the specific roles of helper, regulatory, and cytotoxic T cells in normal cellular immunity.

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1. Helper T cells (CD4+ T cells) are crucial for activating and directing other immune cells. They recognize antigens presented by antigen-presenting cells (APCs) using their T cell receptors (TCRs) and major histocompatibility complex (MHC) class II molecules.
2. Once activated, helper T cells secrete cytokines that stimulate the proliferation and differentiation of B cells into plasma cells and memory B cells, enhancing the humoral immune response.
3. Regulatory T cells (Tregs) are essential for maintaining immune tolerance and preventing autoimmune diseases. They suppress the activation and proliferation of other immune cells, including effector T cells, through the release of inhibitory cytokines like IL-10 and TGF-beta.
4. Cytotoxic T cells (CD8+ T cells) are responsible for directly killing infected or cancerous cells. They recognize antigens presented by MHC class I molecules on the surface of target cells and induce apoptosis through the release of perforin and granzymes.
5. In summary, helper T cells coordinate the immune response, regulatory T cells maintain immune homeostasis, and cytotoxic T cells eliminate infected or abnormal cells, all contributing to effective cellular immunity.

Key Concepts

Helper T Cells

Helper T cells, also known as CD4+ T cells, play a crucial role in the immune response by activating and directing other immune cells. They release cytokines that stimulate B cells to produce antibodies and enhance the activity of cytotoxic T cells and macrophages. This coordination is essential for a robust and effective immune response against pathogens.

Regulatory T Cells

Regulatory T cells, or Tregs, are vital for maintaining immune tolerance and preventing autoimmune responses. They help modulate the immune system by suppressing excessive immune reactions and ensuring that the immune response is appropriately controlled. This balance is crucial for protecting the body from both infections and self-damage.

Cytotoxic T Cells

Cytotoxic T cells, also known as CD8+ T cells, are responsible for directly killing infected or cancerous cells. They recognize specific antigens presented by infected cells and release perforin and granzymes to induce apoptosis in these target cells. Their action is essential for eliminating intracellular pathogens and maintaining cellular integrity.