Question

Fill in the blank

______________ cells circulate through the body searching for infected or cancerous cells by examining
the antigenic determinant on ________ MHC proteins on the cell surface. Fragments of
_______________, degraded proteins are loaded unto these proteins in the endoplasmic reticulum. If the
antigenic peptide is a _____________ antigen, the body cell will be destroyed.

Answer 1

• Cytotoxic T cells circulate through the body searching for infected or cancerous cells by examining the antigenic determinant on MHC class I proteins on the cell surface.
• Fragments of intracellular pathogens, degraded proteins are loaded onto these proteins in the endoplasmic reticulum. If the antigenic peptide is a non-self antigen, the body cell will be destroyed.

Step-by-step explanation:

MHC I molecules, found on all normal, healthy, nucleated cells, signal to the immune system that the cell is a normal 'self' cell. Proteins normally found in the cytoplasm are degraded by proteasomes and processed into self-antigen epitopes. These self-antigen epitopes bind within the MHC I antigen-binding cleft and are presented on the cell surface.

When a cell becomes infected with an intracellular pathogen, pathogen-specific proteins are processed in proteasomes and bind with MHC I molecules for presentation on the cell surface. This signals that the infected cell must be targeted for destruction along with the pathogen.