Which cell type can act as an antigen-presenting cell for exogenous antigens?

Which cell type can act as an antigen-presenting cell for exogenous antigens?

• A. All nucleated cells
• B. Endothelial cells
• C. B lymphocytes
• D. T lymphocytes

Answer: (C)

Exogenous antigen presentation relies on presenting peptide fragments on MHC class II to CD4+ T helper cells. B lymphocytes are capable of acting as antigen-presenting cells for these antigens because they can bind specific antigen via their B cell receptor, internalize it, process it, and display the resulting peptides on MHC II. They also upregulate costimulatory molecules upon activation, making the T cell activation signal robust. In contrast, most other nucleated cells mainly present endogenous peptides on MHC I to CD8+ T cells and aren’t optimized for presenting exogenous antigens; T cells themselves don’t present antigen to other T cells.

Exogenous antigen presentation relies on presenting peptide fragments on MHC class II to CD4+ T helper cells. B lymphocytes are capable of acting as antigen-presenting cells for these antigens because they can bind specific antigen via their B cell receptor, internalize it, process it, and display the resulting peptides on MHC II. They also upregulate costimulatory molecules upon activation, making the T cell activation signal robust. In contrast, most other nucleated cells mainly present endogenous peptides on MHC I to CD8+ T cells and aren’t optimized for presenting exogenous antigens; T cells themselves don’t present antigen to other T cells.