Immunology T Cell Activation Quiz

Cellular Immune Response I Lecture Notes

• Lecture Outline: The lecture covers the main phases of T lymphocyte responses, antigen recognition, activation signals, CD8+ T cell activation, functional responses of activated T lymphocytes, memory T cells, and T lymphocyte migration to infection sites.

• T Lymphocyte Responses Phases: The lecture outlines the stages involved in T lymphocyte responses.

• Antigen Recognition by T Lymphocytes: The role of CD4, CD8, and adhesion molecules is crucial to antigen recognition by T lymphocytes.

• CD4+ T Lymphocyte Activation: Activation signals and co-stimulation molecules are essential for CD4+ T lymphocyte activation.

• CD8+ T Lymphocyte Activation: The mechanisms of activating CD8+ T lymphocytes are described.

• Activated T Lymphocyte Functional Responses: The lecture details the functional responses of activated T lymphocytes.

• Memory T Lymphocyte Features: The lecture explores the characteristics of memory T lymphocytes, and their significance in the immune response.

• Effector T Lymphocyte Migration: The process by which effector T lymphocytes migrate to infection sites is examined.

Types of Intracellular Microbes and T Cell-Mediated Immunity

• T Cell-Mediated Immunity (CMI): T lymphocytes play a vital role in CMI, providing defense against infections caused by intracellular microbes.

• Intracellular Microbes: There are two types of infections caused by intracellular microbes: phagocytosis by phagocytes in immunity's early defense phase, and the microbes that can resist phagocytosis, and the microbes that infect the cell cytoplasm.

Objectives

• Objective 1: This objective asks what the main phases of T lymphocyte responses are.

• Objective 2a: This objective aims to describe how T lymphocytes recognize antigens.

• Objective 2b: This objective investigates the role of CD4, CD8, and adhesion molecules.

• Objective 4: This objective focuses on the activation mechanisms of CD8+ T lymphocytes.

• Objective 5: This objective details the functional responses of T cells after activation, including cytokine production, clonal expansion, and differentiation into effector cells.

• Objective 6: This objective is the end point of the cellular immune response, where the immune system returns to a steady state after clearing an infection.

• Objective 7: How effector T cells migrate to an infection site.

T Cell Activation and Costimulation

• How T Cells Recognize Ags: The initial step in T cell responses involves multiple receptors on the T cell engaging ligands on antigen-presenting cells (APCs).

• T-Cell Activation Signals: T cell activation entails recognition of antigen-MHC complexes, co-receptor interactions, adhesion molecules to strengthen the binding, and the involvement of costimulatory receptors in the activation process.

Surface Molecules of T Cells

• T Cell Surface Molecules: The key surface molecules of T lymphocytes are detailed for their roles in the functional responses.

T Cell Activation: Costimulation

• T Cell Activation: T cell activation is dependent on antigen, and also requires costimulation from APCs.

• Normal and Abnormal T Cell Activation: During normal activation, APCs express costimulators to activate T cells, whereas resting APCs, lack this expression, leading to T cell tolerance.

How are CD8+ T Lymphocytes Activated?

• Activation of CD8+ T Cells: The activation of CD8+ T cells follows a similar activation path to CD4+ T cells, involving dendritic cells or infected tissue cells and presenting microbe-derived antigens, costimulation, and helper T cells, which stimulate the expansion and differentiation of CD8 T cells.

How are T-Cells Fully Activated?

• T Cell Activation Pathways: T cell activation involves a series of steps initiated by antigen recognition, resulting in enzyme activation, recruitment of adaptor proteins, and production of active transcription factors on the surface of antigen-presenting cells (APCs).

What are the Functional Responses of T Cells after Activation

• Functional T Cell Responses Post Activation: Following T cell activation, a series of functional responses occur within 1-2 hrs or up to 3-4 days, including cytokine production, clonal expansion, and differentiation into effector cells.

Memory T Lymphocytes

• Memory T Lymphocytes: Memory T cells survive infection clearance and can be found in lymphoid organs, peripheral tissues, and the bloodstream. They can rapidly respond to subsequent infections of the same pathogen.

End Point of Cellular Immune Response

• Homeostasis after Immune Response: After clearing an infection, the immune system returns to a stable state by eliminating excess T cells via apoptosis and by retaining memory cells. 

Migration of Effector T Cells

• Effector T Cell Migration: Effector T cells migrate to infection sites, guided by adhesion molecules like L-selectin and chemokine receptors. They preferentially target sites where the infection has occurred.

Test your knowledge about T cell activation and the roles of various receptors and cytokines. This quiz covers interactions between T cells and MHC, the importance of IL-2, and co-stimulation. Perfect for students or enthusiasts in immunology.