T Cells and T Cell Receptors Quiz

T Cells and T Cell Receptors

• T cells are crucial for the adaptive immune system, specializing in cell-mediated immunity.
• T cells recognize specific peptide antigens presented by major histocompatibility complex (MHC) molecules.
• T cells come in different types, including cytotoxic T cells and helper T cells (e.g., TH1, TH2, TFH).
• Effector functions of T cells include inducing cell death, activating macrophages, mediating anti-parasitic responses, and B cell activation.
• T cell activity relies on interactions between T cell receptors (TCRs) on T cells and MHC-peptide complexes on target cells.

T Cell Receptor (TCR)

• TCR is a protein complex comprising TCR itself and associated proteins.
• TCR is formed by two polypeptide chains (e.g., alpha and beta).
• Associated CD3 proteins enhance signaling.
• Co-receptors (e.g., CD4 or CD8) are necessary for ligand recognition.
• T cells are divided into CD4+ and CD8+ subsets.
• ITAMs (Immunoreceptor Tyrosine-based activation motifs) are essential components of the TCR signaling pathway.

TCR vs. B Cell Receptor

• TCRs are solely membrane-bound.
• TCR antigen binding is weaker than antibody binding.
• Antigens recognized by T cells are presented by MHC molecules.

TCR Diversity

• TCR diversity is generated through combinatorial joining of V(D)J gene segments, junctional flexibility, P-region, and N-region nucleotide additions. These mechanisms mimic Ig (immunoglobulin) diversity.
• TCRs lack somatic mutations, which maintain their specificity after thymic selection, preventing self-reactive T cells.

T Cell Receptor Ligands

• MHC proteins present antigenic peptide fragments.
• MHC proteins are classified as MHC class I and II.
• MHC class I is found on all nucleated cells.
• MHC class II is found on antigen-presenting cells (APCs).
• CD8 co-receptors bind invariant parts of MHC class I.
• CD4 co-receptors bind invariant parts of MHC class II.
• T cells must distinguish between self and non-self peptides.

Alloreactivity

• Alloreactivity refers to the T cells' response to genetically different individuals (even of the same species).
• T cells typically respond to antigen presented by MHC molecules.
• However, T cells can recognize foreign MHC molecules, as seen in transplant rejection.

Test your knowledge about T cells and T cell receptors, key components of the adaptive immune system. This quiz covers the functions, types, and mechanisms of T cells, including the interactions of TCRs with MHC molecules. Dive into the specifics of T cell mediators and their importance in immune responses.