Antigen Recognition by T Lymphocytes

These flashcards cover key concepts of T lymphocyte antigen recognition, T-cell development, the role of dendritic cells, and significant aspects of the immune system as discussed in the lecture notes.

What chains are covalently attached in T-Cell antigen recognition?

The alpha (a) and beta (b) chains.

What is a key difference between antibodies and T-cell receptors (TCR)?

Antibodies lack a transmembrane domain and are soluble, while TCRs are membrane-bound.

How many binding sites do TCRs have?

One binding site.

What regions do both TCR alpha and beta chains contain?

Constant and variable regions.

What is the function of Major Histocompatibility Complex (MHC) Class I?

To present intracellular antigens to CD8+ cytotoxic T-cells.

What type of antigens do MHC Class II molecules present?

Extracellular antigens.

What is the role of CD8 coreceptors?

CD8 coreceptors are specific to cytotoxic T-cells and help with signal transduction.

What is a significant evolutionary mechanism that allowed for gene duplication in TCR and immunoglobulin genes?

Transposons allowed for the movement, duplication, and rearrangement of germline configurations.

What is the role of dendritic cells in T-cell activation?

Dendritic cells present antigens and are critical for the activation of naive T-cells.

What does positive selection in T-cell development involve?

The interaction of TCR with specific MHC molecules determines if a T-cell matures to CD4 or CD8.

How is TCR signal transduction initiated upon antigen recognition?

Signaling is initiated by the phosphorylation of ITAMs in the CD3 complex and zeta chains.

What does the term 'MHC restriction' refer to?

A T-cell can only recognize peptides presented by the specific type of MHC it was selected to bind.

What is the outcome if a T-cell does not successfully undergo positive selection?

The T-cell will continue to rearrange its alpha chain until it either succeeds or dies by apoptosis.

What type of receptors do T-cells express during negative selection?

They express receptors that interact moderately with MHC to avoid autoimmunity.

Which cytokine is crucial for T-cell proliferation and functional differentiation?

IL-2.

In what way do cytotoxic T-cells induce apoptosis in target cells?

By inducing apoptosis through lytic granules and Fas ligand interactions.

How do CD4+ T-helper cells enhance the function of macrophages?

By increasing CD40 and IFN-gamma receptors for enhanced cell contact and enzyme production.

What do regulatory T-cells (Tregs) do during T-cell development?

They suppress the activity of potentially self-reactive T-cells to prevent autoimmune diseases.

What impact does HLA genetic variation have on immunity?

Higher diversity in HLA leads to better recognition of diverse antigens, aiding in the immune response.