Fig 1.
Overview of T cell activation by streptococcal superantigens and functional outcomes.
Displayed are cartoons showing a comparison of conventional versus superantigen-mediated T cell activation, and a ribbon diagram of the SpeA superantigen (gray) in complex with the TCR expressed on a T cell (yellow) and MHC-II expressed on an APC (blue). Compared with convention T cell activation, note how the superantigen engages the β-chain of the TCR and displaces the TCR away from the MHC-II presented antigenic peptide (black) leading to the Vβ-specific activation of T cells. The structural model was generated using the co-crystal structure of SpeA in complex with mouse Vβ8 (PDB code 1L0Y) and superimposing a human αβ TCR (PDB code 1FYT) and human MHC-II from the staphylococcal enterotoxin C3 superantigen in complex with HLA-DR1 (PDB code 1JWM). The ribbon diagram was generated using PyMOL Molecular Graphics System (https://pymol.org). APC, antigen presenting cell; MHC-II, MHC class II molecule; TCR, T cell receptor.