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Cell Immunol. 1998 Nov 25;190(1):51-60.

The function of TGF-beta-mediated innocent bystander suppression associated with physiological self-tolerance in vivo.

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Department of Microbiology & Immunology, the University of Western Ontario, London, Ontario, N6A 5C1, Canada.


Innocent bystander suppression has been demonstrated in experimental models of transplantation tolerance and oral tolerance. This phenomenon is associated with expression of cytokines such as TGF-beta or/and type II cytokines (e.g., IL-4, IL-10). However, the mechanism responsible for bystander suppression is poorly understood, as is its role in antigen-specific self-tolerance. Here, we describe a series of investigations using an antigen coimmunization strategy to examine the outcome of bystander suppression in vivo in a well-characterized physiological model, using beef insulin transgenic (BI-Tg) mice, for self-tolerance. Our results demonstrate that: (1) T-cell-mediated peripheral hyporesponsiveness, or CD4(+) regulatory type II Th cell-mediated adoptive transfer of peripheral hyporesponsiveness (defined by an ELISA antibody assay), is antigen-specific at induction but effector-nonspecific (bystander suppression) when the self-antigen (BI) and a control antigen (chicken ovalbumin) are coadministered in BI-Tg mice; (2) bystander suppression is manifest as a local and transient, rather than a systemic and long-term, phenomenon; (3) bystander suppression is both time and antigen dose dependent; and (4) anti-TGF-beta Mab abolishes the effect of bystander suppression in vivo. We suggest that TGF-beta-mediated innocent bystander suppression associated with physiological self-tolerance thus produces no major biological consequence for general immune responsiveness. It may prevent the activation of auto(or cross)-reactive lymphocytes.

[Indexed for MEDLINE]

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