Non-peptidic antigen
（重定向自Phosphoantigen）
Non-peptidic antigens are low-molecular-weight compounds that stimulate human Vγ9/Vδ2 T cells. The most potent activator for Vγ9/Vδ2 T cells is (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), a natural intermediate of the non-mevalonate pathway of isopentenyl pyrophosphate (IPP) biosynthesis. HMB-PP is an essential metabolite in most pathogenic bacteria including Mycobacterium tuberculosis as well as in malaria parasites, but is absent from the human host.