MHC class II molecules are expressed on which cells?

MHC class II molecules are expressed on which cells?

• A. B cells
• B. Neurons
• C. Erythrocytes
• D. Professional antigen-presenting cells

Answer: (D)

MHC class II molecules are used by cells that specialize in presenting extracellular antigens to CD4+ T helper cells. They are expressed on professional antigen-presenting cells, including dendritic cells, macrophages, and B cells. These cells take up external proteins, process them in endosomes, and display peptide fragments on MHC II to activate helper T cells, coordinating the immune response. Neurons generally do not express MHC II, and mature erythrocytes lack antigen-processing machinery, so they do not present antigens via MHC II. Therefore, the correct category is professional antigen-presenting cells.

MHC class II molecules are used by cells that specialize in presenting extracellular antigens to CD4+ T helper cells. They are expressed on professional antigen-presenting cells, including dendritic cells, macrophages, and B cells. These cells take up external proteins, process them in endosomes, and display peptide fragments on MHC II to activate helper T cells, coordinating the immune response. Neurons generally do not express MHC II, and mature erythrocytes lack antigen-processing machinery, so they do not present antigens via MHC II. Therefore, the correct category is professional antigen-presenting cells.