Q.7 Endogenous antigens are presented on to the cell surface along with
(A) MHC-II (B) MHC-I (C) Fcγreceptor (D) complement receptor
Endogenous antigens from intracellular sources like viruses or self-proteins display on cell surfaces via MHC class I molecules to alert cytotoxic T cells. This MCQ tests core immunology concepts vital for biotech, vaccine design, and infectious disease research.
Correct Answer
(B) MHC-I presents endogenous antigens. Intracellular proteins degrade in cytosol via proteasome, peptides transport into ER by TAP, load onto MHC-I, then traffic to surface for CD8+ T cell recognition.
Option Analysis
(A) MHC-II
MHC-II handles exogenous antigens from extracellular pathogens, processed in endosomes by APCs like dendritic cells for CD4+ T helper activation.
(C) Fcγ Receptor
Fcγ receptors bind antibody Fc regions on immune cells, facilitating phagocytosis and ADCC but not peptide antigen presentation.
(D) Complement Receptor
Complement receptors (CR1/CR3) mediate opsonized particle uptake and B cell modulation, unrelated to endogenous peptide display.
Pathway Essentials
The cytosolic MHC-I route ensures surveillance of infected or malignant cells: 8-10 residue peptides stabilize MHC-I, triggering perforin/granzyme-mediated lysis. Cross-presentation allows dendritic cells to show exogenous antigens on MHC-I too.
