Protocols to Study Effects of Shiga Toxin on Mononuclear Leukocytes

Endothelial cells are regarded as the main targets of the Shiga toxins (Stxs) during infections caused by Stx-producing Escherichia coli (STEC). However, several investigations also confirmed an effect of these toxins on immune cell functions in species naturally infected with STEC. Human B-cell lines (1 ) and tonsillar B-cells (2 ) are highly susceptible to the cytotoxic activity of Stx1, which also hampers activation and proliferation of bovine B- and T- cell subpopulations in vitro (3 ). Although Stxs appear to be immunosuppressive, they do not prevent the development of a specific antibody response in STECinfected individuals (4 –6 ). Thus, the question of an immunosuppressive effect of Stx in the pathogenesis of STEC-mediated diseases needs to be addressed. STEC infections lead to an immunocompromised condition in gnotobiotic pigs and calves (7 ,8 ), which is assumed to contribute to the observed persistency of infection (e.g., in calves and humans) (9 ,10 ).