Cell-mediated immunity

Definition

Cell-mediated immunity is a crucial component of the adaptive immune response that relies on the activation of T cells to combat intracellular pathogens and cancer cells. This form of immunity is distinct from humoral immunity, as it focuses on direct cell-to-cell interactions rather than the production of antibodies. Through the actions of various T cell subsets, such as cytotoxic T cells and helper T cells, cell-mediated immunity plays a vital role in protecting the body from infections and maintaining immunological memory.

5 Must Know Facts For Your Next Test

1. Cell-mediated immunity is particularly effective against viruses, intracellular bacteria, and tumor cells, where antibodies alone are insufficient to eliminate the threat.
2. Cytotoxic T cells directly attack infected or malignant cells by recognizing specific antigens presented by major histocompatibility complex (MHC) molecules on their surfaces.
3. Helper T cells enhance the immune response by secreting cytokines that stimulate other immune cells, including B cells and cytotoxic T cells.
4. Immunological memory in cell-mediated immunity allows for a quicker and stronger response upon re-exposure to previously encountered antigens.
5. Vaccinations can enhance cell-mediated immunity by promoting the development of memory T cells, providing long-term protection against specific pathogens.

Review Questions

• How does cell-mediated immunity differ from humoral immunity in terms of mechanisms and types of pathogens targeted?
  • Cell-mediated immunity primarily involves T cells that directly interact with infected or abnormal cells to eliminate them, while humoral immunity is characterized by the production of antibodies by B cells. Cell-mediated immunity is particularly effective against intracellular pathogens like viruses and certain bacteria, whereas humoral immunity mainly targets extracellular pathogens. This distinction highlights the complementary roles both types of immunity play in protecting the body from various infections.
• Discuss the role of cytokines in enhancing cell-mediated immunity and how they facilitate communication among immune cells.
  • Cytokines are essential signaling molecules in cell-mediated immunity that mediate communication between various immune cells. They help coordinate the immune response by influencing T cell activation, proliferation, and differentiation. For instance, helper T cells release specific cytokines that stimulate cytotoxic T cells and enhance B cell responses. This intricate signaling network ensures that the immune system mounts a robust response against pathogens while also maintaining homeostasis.
• Evaluate how immunological memory generated from previous infections or vaccinations contributes to more effective cell-mediated immune responses upon subsequent exposures.
  • Immunological memory plays a pivotal role in enhancing the efficiency of cell-mediated immune responses during subsequent exposures to pathogens. When an individual is first exposed to a pathogen, memory T cells are generated alongside effector T cells. Upon re-exposure, these memory T cells can rapidly recognize the pathogen's antigens, leading to a quicker and more potent activation of cytotoxic T cells and helper T cells. This accelerated response often results in faster clearance of infections and reduced severity of disease compared to the primary response.

Related terms

T cells: A type of white blood cell that plays a central role in cell-mediated immunity, responsible for recognizing and eliminating infected or abnormal cells.

Cytokines: Signaling molecules produced by immune cells that facilitate communication and coordination among immune responses, including those involved in cell-mediated immunity.

Antigen presentation: The process by which immune cells display antigens on their surfaces to activate T cells, initiating the adaptive immune response.