Class I MHC antigens E and G serve which function?

Class I MHC antigens E and G serve which function?

• A. Enhance the response by macrophages
• B. Transport antigen for recognition by CD4+ T cells
• C. Bind to A, B, and C antigens to protect the binding site
• D. Protect fetal tissue from destruction by NK cells

Answer: (D)

These non-classical MHC class I molecules have a regulatory role at the maternal–fetal interface. HLA-E and HLA-G help protect fetal tissue from destruction by natural killer (NK) cells by delivering inhibitory signals to maternal NK cells. HLA-E interacts with the NK cell receptor CD94/NKG2A, and HLA-G binds inhibitory receptors such as LILRB1 on NK cells. This engagement dampens NK cell cytotoxicity, promoting tolerance of the fetus despite paternal antigens. This isn’t about presenting peptides to CD8+ T cells (that’s the typical role of classical MHC I), nor about enhancing macrophage activation, nor about some nonspecific binding protection. So the protective, inhibitory role against NK cells during pregnancy is the best fit.

These non-classical MHC class I molecules have a regulatory role at the maternal–fetal interface. HLA-E and HLA-G help protect fetal tissue from destruction by natural killer (NK) cells by delivering inhibitory signals to maternal NK cells. HLA-E interacts with the NK cell receptor CD94/NKG2A, and HLA-G binds inhibitory receptors such as LILRB1 on NK cells. This engagement dampens NK cell cytotoxicity, promoting tolerance of the fetus despite paternal antigens.

This isn’t about presenting peptides to CD8+ T cells (that’s the typical role of classical MHC I), nor about enhancing macrophage activation, nor about some nonspecific binding protection. So the protective, inhibitory role against NK cells during pregnancy is the best fit.