Question

T/F: Allelic exclusion of the T-cell receptor α and β chains is effective; therefore, all T cells express only one T-cell receptor on the cell surface.

Answer 1

It is true that all T cells express only one T-cell receptor on their surface due to allelic exclusion, which ensures a single T cell expresses one alpha and one beta chain, allowing for antigen specificity.

Step-by-step explanation:

The statement that all T cells express only one T-cell receptor on the cell surface is true. T cell receptors (TCRs) are unique in that each T cell produces only one type of receptor which is specific for a single particular antigen. Allelic exclusion ensures that a single T cell expresses only one alpha chain and one beta chain, preventing the expression of additional TCRs.

The antigen-specific part of a TCR consists of variable regions of both the alpha and beta chains that bind to processed antigens via the Major Histocompatibility Complex (MHC) on antigen-presenting cells (APCs). The alpha-beta T cell receptors are the most common and the diversity in their amino acid sequences in the variable domains allows them to recognize a myriad of antigens.