B.1.617.2/Delta variant mutation sites include(47): T19R, G142D, E156G, F157Δ, R158Δ, L452R, T478K, D614G, P681R, D950N. Table shows that G142D, E156G, F157Δ, and R158Δ are all in the MHC_II_alpha A, MHC_II_beta B, MHC_I-like_Ag-recog B domains. Both G142D and E156G are in the MHC_I_2 A domain. E156G, F157Δ, and R158Δ are all located in the MHCassoc_trimer A domain. Other mutation sites are not in the MHC-like domain. These four MHC-like domains are highly overlapping. Combining these four MHC-like domain sites, the MHC-like enhanced distribution area of B.1.617.2/Delta variant S protein is 127-194. It is in the N-terminal domain (14-305 residues, the S1 protein region) . Among them, MHCassoc_trimer (144-162) plays an essential role in forming S trimer. The MHC-like enhanced distribution area of the S protein has MHC-I_like and MHC-II_like functions, so it can also bind to CD4+ T, CD8+ T, NK cells.