超抗原（superantigen）

超抗原的主要特性

通过与APC 上MHC分子和TCR双方结合，激活相应T细胞克隆

激活T细胞
无需APC加工
无MHC限制性
非特异性，多克隆激活

两类:外源性超抗原如葡萄球菌肠毒素A-E等内源性超抗原狂犬病毒-核衣壳蛋白

另外,热休克蛋白(heat shock protein, HSP)和金黄色葡萄球菌蛋白 A(staphylococcus protein A, SPA) 分别是刺激 TCRyd +T和B 细胞的SAg。
attachment/AttachedPic/超抗原.png

attachment/AttachedPic/Superantigen.png

Superantigens are molecules, frequently toxic products of bacteria, that bind MHC molecules on the cell surface and are then presented to a large subset of T cells, usually defined by the expression of a particular family of TCR V regions. ——Paul's

Most of the known superantigens bind MHC-II molecules, though one, the agglutinin from Urtica dioica, the stinging nettle, can be bound by both MHC-I and MHC-II molecules and presented to T cells of the Vβ8.3 family.

大多数已知的超抗原都能结合MHC-II分子，尽管有一种，来自荨麻的凝集素，可以被MHC-I和MHC-II两种分子结合，并呈递给Vβ8.3家族的T细胞

2*4=8，MHC-II分子与CD4+T细胞结合（Helper T cell）_{CD8+T细胞为细胞毒性T细胞}