Which statement about self-nonself distinction is true according to the described role of MHC proteins?

Which statement about self-nonself distinction is true according to the described role of MHC proteins?

• A. MHC Proteins Identify Pathogens Directly.
• B. MHC Proteins Distinguish 'Self' from 'Nonself'.
• C. MHC Proteins Trigger Antibody Production.
• D. MHC Proteins Coordinate Cytokine Release.

Answer: (B)

MHC proteins enable the immune system to tell self from nonself by presenting peptide fragments on the surface of cells. T cells scan these peptide–MHC complexes and interpret them to decide whether the fragment originates from the organism itself or from a foreign source such as a pathogen. This presentation framework is what allows immune responses to target invaders while avoiding attack on the body’s own tissues. MHC molecules don’t identify pathogens directly, nor do they initiate antibody production on their own. Antibody production is carried out by B cells, usually after receiving help from activated T cells that have recognized a foreign peptide presented by MHC. Cytokine release is a downstream effect of immune activation, driven by those activated cells, not a direct function of MHC molecules themselves.

MHC proteins enable the immune system to tell self from nonself by presenting peptide fragments on the surface of cells. T cells scan these peptide–MHC complexes and interpret them to decide whether the fragment originates from the organism itself or from a foreign source such as a pathogen. This presentation framework is what allows immune responses to target invaders while avoiding attack on the body’s own tissues.

MHC molecules don’t identify pathogens directly, nor do they initiate antibody production on their own. Antibody production is carried out by B cells, usually after receiving help from activated T cells that have recognized a foreign peptide presented by MHC. Cytokine release is a downstream effect of immune activation, driven by those activated cells, not a direct function of MHC molecules themselves.