Question

T-cell receptors interact not only with peptide anchored in the peptide-binding groove of MHC molecules, but also with ________?

1) B cells
2) Antibodies
3) Cytokines
4) Co-stimulatory molecules

Answer 1

T-cell receptors interact with peptides presented by MHC molecules and co-stimulatory molecules for their activation, with co-stimulatory molecules being the direct answer to the student's question.

Step-by-step explanation:

The T-cell receptors (TCR) interact not only with peptides anchored in the peptide-binding groove of MHC molecules, but also with co-stimulatory molecules. This interaction is crucial for the activation of T-cells.

T-cell receptors are specific to antigen fragments coupled with Major Histocompatibility Complex (MHC) molecules. There are two types of MHC molecules, MHC I, which is found on all nucleated cells, and MHC II, which are mainly present on antigen-presenting cells (APCs). Naïve T-cells express either the CD4+ or CD8+ molecule, which influences whether their TCR will bind to MHC II or MHC I, respectively. CD4+ T cells, also known as helper T cells, primarily interact with APCs via MHC II, while CD8+ cells, or cytotoxic T cells, engage with MHC I on infected cells, leading to their activation. For full activation, T cells also require engagement with other molecules on APCs known as co-stimulatory molecules. These molecules are essential for a robust and complete T-cell response and are a key part of the immune system's ability to respond effectively to pathogens.