a super antigen is a bacterial product that

Ref Harrison 16/e p1920 Superantigens (SAgs) are a class of antigens that result in excessive activation of the immune system. Specifically it causes non-specific activation of T-cellsresulting in polyclonal T cell activation and massive cytokine release. SAgs are produced by some pathogenic viruses and bacteria most likely as a defense mechanism against the immune system.Compared to a normal antigen-induced T-cellresponse where 0.0001-0.001% of the body's T-cells are activated, these SAgs are capable of activating up to 20% of the body's T-cells. Fuhermore, Anti-CD3and Anti-CD28 Antibodies (CD28-SuperMAB) have also shown to be highly potent superantigens (and can activate up to 100% of T cells).