MHC class 1 molecules present which type of antigens?

MHC class I molecules are crucial components of the immune system, specifically involved in presenting antigens to CD8+ T cells, also known as cytotoxic T lymphocytes. These molecules primarily present peptides derived from proteins that are synthesized within the cell, which typically include those produced by intracellular pathogens, such as viruses and some bacteria.

When cells are infected by an intracellular pathogen, these pathogens replicate inside the host cell, leading to the production of viral or bacterial proteins. The processing of these proteins involves their breakdown into small peptides, which are then transported into the endoplasmic reticulum. In this location, MHC class I molecules bind these peptides and are transported to the cell surface. This presentation allows CD8+ T cells to recognize and respond to infected cells by initiating a cytotoxic response, thus playing a critical role in the adaptive immune response against infections.

The other types of antigens listed in the options have different presentation mechanisms. Extracellular pathogens typically involve MHC class II molecules, which present peptides derived from extracellular proteins to CD4+ T cells. Allergen-associated antigens can also be presented by MHC class II molecules. Autoantigens, which can arise from the body’s own proteins, may be presented by MHC class