MECHANISMS UNDERLYING T-CELL TOLERANCE

To understand how the immune system manages to disarm potentially harm ful T cells with reactivity against self-antigens, many immunologists have turned to model systems in which transgenic expression of TCRs, f oreign antigens, or both, allows visualization of otherwise undetectab le mechanisms. Recent data have offered several new insights into the variables that dictate the mechanism for tolerance employed by periphe ral T cells. Some of these mechanisms can also dampen ongoing immune r esponses against foreign antigens and provide a strikingly powerful su pplement to the primary mechanism of tolerance, thymic clonal deletion .