Cell-mediated immune response

Cell-mediated immune response is a type of immune response that involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. This immune response is primarily regulated by T cells, and it is vital for the elimination of pathogens that survive within cells, including viruses and bacteria, as well as for fighting fungal infections, cancer cells, and foreign tissues (in transplant rejection, for example).

Overview

The cell-mediated immune response begins when macrophages present antigens to T helper cells. This interaction stimulates the T helper cells to release cytokines, which in turn activate other immune cells such as cytotoxic T cells and natural killer cells. These cells then directly attack the infected or abnormal cells.

Antigen Presentation

In the cell-mediated immune response, antigen presentation is a vital process. Antigens are proteins that the immune system recognizes as foreign. Macrophages and dendritic cells are examples of antigen-presenting cells that engulf pathogens and present their antigens on their surface to T cells.

T Cells and Cytokines

T cells play a central role in the cell-mediated immune response. They are activated when they recognize antigens presented by antigen-presenting cells. Once activated, T cells proliferate and differentiate into effector T cells, which can directly kill infected cells or help activate other immune cells.

Cytokines are signaling molecules that are crucial for the cell-mediated immune response. They are produced by T cells and other immune cells and act to regulate the immune response. Different types of cytokines have different effects, such as promoting inflammation, inducing cell death, or stimulating cell proliferation.

Cytotoxic T Cells and Natural Killer Cells

Cytotoxic T cells and natural killer cells are the main effector cells in the cell-mediated immune response. Cytotoxic T cells recognize and kill infected cells directly, while natural killer cells can kill infected cells without prior sensitization to the specific antigen.

Clinical Significance

The cell-mediated immune response is crucial for the body's defense against intracellular pathogens, such as viruses and some bacteria. It is also important in controlling and eliminating cancer cells. However, an overactive or misdirected cell-mediated immune response can lead to autoimmune diseases, where the immune system attacks the body's own cells.