Immunology I - T Lymphocytes and Antigen Recognition

Flashcards about T cells, T cell receptors, MHC molecules, and associated immune responses.

What are the two major populations of lymphocytes involved in adaptive immunity?

B lymphocytes (B cells) and T lymphocytes (T cells)

Where do T cells originate and mature?

They are born from hematopoietic stem cells in the bone marrow and mature in the thymus gland.

What is cell-mediated immunity?

The immune response mediated by T cells, also known as T-cell mediated immunity.

What are the different receptors expressed on the surface of T cells?

CD3, CD4 (Helper T lymphocytes), CD8 (Cytotoxic T lymphocytes), CD28 (receptor for antigen-presenting cells), and CD45 (receptor for signaling of immune cells).

How are antigens presented to T cells?

Antigens must be presented via antigen-presenting cells with the help of Major Histocompatibility Complex (MHC) molecules.

Give some examples of antigen-presenting cells.

Macrophages, B cells, dendritic cells, neutrophils, basophils, eosinophils, and platelets.

What is the function of antigen-presenting cells?

To cleave or process antigens into smaller fragments (epitopes) and express them on MHC molecules.

What are the two classes of MHC molecules?

MHC-class I and MHC-class II.

Which T cell receptors do MHC-class I molecules bind to?

CD8 T cell receptors (cytotoxic T cells).

Which T cell receptors do MHC-class II molecules bind to?

CD4 T cell receptors (Helper T cells).

What is the function of MHC-class I molecules?

To enable the recognition of infected cells and their destruction by cytotoxic CD8 T cells.

Where are MHC-I molecules present?

Lymphocytes (B cells), neutrophils, basophils, eosinophils and platelets

Where are MHC-II molecules present?

professional antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B- lymphocytes

What is the length of antigen epitopes that MHC-class I can bind?

8-9 amino acids long.

What happens when CD8 T cells bind to the MHC-class I molecule?

They form a MHC: antigen peptide complex that will help to kill the antigen.

What are anchor residues?

Amino acid residues on the antigen that allow it to attach tightly into the groove of the MHC molecule.

What is the function of MHC-class II molecules?

To enable CD4 T cells to recognize antigen peptides (epitopes) and initiate the release of cytokines and immune cells to kill the antigen.

What is the length of antigen epitopes that MHC-class II can bind?

12-17 amino acids long.

How do CD4 T cells respond to MHC-class II molecules?

They bind to these MHC-class II molecules and form an MHC: antigen peptide complex that will initiate an immune response against the antigen.

What are the two transmembrane glycoprotein chains that form the T-cell receptor?

α chain and β chain.

What is the variable region (V) and what is its function?

It is a highly variable region in the amino terminus that contains hypervariable or complementarity determining regions (CDR) that serve as antigen binding sites.

What is the role of CD4 and CD8 receptors in T cells?

Both are involved in antigen binding and signal transmission for stimulating an immune response against the antigen.

How do CD8 T cells kill infected cells?

Secretion of cytokines, production and release of cytotoxic granules (perforin and granzymes), and apoptotic cell death through Fas molecules.

What cytokines are secreted by CD8 T cells?

Tumor necrosis factor-alpha (TNF-α) and Interferon-gamma (IFN-γ).

How do perforins and granzymes function?

Perforins create pores in the lipid bilayer of the antigen, allowing granzymes to enter and degrade the antigen's cellular DNA.

What is apoptosis?

Programmed cell death, characterized by nuclear blebbing, alteration in cell morphology, and fragmentation of DNA.

What are the dual functions of CD4 T cells?

Activating immune cells for antigen killing and suppressing the immune response once the antigen has been eliminated.

What is the role of pro-inflammatory cytokines released by CD4 T cells?

activating the cells of the innate immune system, B-lymphocytes and cytotoxic CD8 T cells

What is severe combined immunodeficiency (SCID)?

An immunodeficiency disease characterized by the combined absence of T and B lymphocyte function.