 Additionally, culturing bacteria "in vitro" provides an environment which is rich in nutrients, in contrast to the reality of an "in vivo" environment, in which nutrients tend to be more scarce.TSST-1 can be purified by preparative isoelectric focusing for use "in vitro" or for animal models using a mini-osmotic pump.A superantigen such as TSST-1 stimulates human T cells that express VB 2, which may represent 5-30% of all host T cells.