T-cell clones in an individual recognize peptides only when bound and displayed by that individual's MHC molecules on the surface of antigen…
T-cell clones in an individual recognize peptides only when bound and displayed by that individual's MHC molecules on the surface of antigen presenting cells. This process is known as:
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Correct Answer: Option B
Explanation
MHC restriction of T cells:MHC (Major Histocompatibility Complex) restriction means that T lymphocytes can only recognise foreign antigens when presented by SELF-MHC molecules on the surface of antigen-presenting cells (APCs):• CD8+ cytotoxic T cells: recognise peptides presented by MHC class I (on all nucleated cells).• CD4+ T helper cells: recognise peptides presented by MHC class II (on professional APCs: dendritic cells, macrophages, B cells).This restriction is established during T cell development in the THYMUS:• Positive selection: T cells that can recognise SELF-MHC (regardless of peptide) survive.• Negative selection: T cells that bind self-MHC+self-peptide too strongly are eliminated (prevents autoimmunity).Significance: MHC restriction ensures that T cells only respond to foreign antigens presented by cells of the same individual, not in isolation.Answer: T cells recognise foreign peptides only when presented by self-MHC molecules.