Once the GAS has penetrated the epithelial barrier, the actions of bacterial exotox- ins damage the host cell and provoke immune responses. Haemolysins destroy host cells and induce antibody produc- tion. Streptococcal pyrogenic exotoxins (SPEs) induce fever (and rash in scarlet fever) and strongly activate the im mune system. In toxic shock syndrome, it is these exotoxins that are believed to act as "superantigens", triggering widespread abnormal activation of immune and inflammatory responses., other exotoxins cause the formation of pus, which provides a growth medium for the bacteria, and enzymes that allow further penetration of the GAS through the host connective tissue