Affiliation:
1. Institute of Microbiology and Immunology, School of Medicine, Belgrade
Abstract
The main function of the immune system is to protect the body by responding
to invading microorganisms. Immunologic tolerance is the basic property of
the immune system that provides for self/non-self discrimination so that the
immune system can protect the host from external pathogens without reacting
against itself. Central tolerance is achieved by the clonal deletion of
self-reactive lymphocytes expressing receptors with high avidity for self.
Autoreactive lymphocytes which escaped selection in the central lymphoid
organs are present in the peripheral repertoire but but are kept under
control by multiple diverse peripheral tolerance mechanisms acting either
directly on the self-reactive T cell (T-cell intrinsic) or indirectly via
additional cells (T-cell extrinsic). Intrinsic mec hanisms include ignorance
of autoantigens, anergy, phenotype skewing or activation-induced cell death
of autoreactive T lymphocytes, while extrinsic mechanisms act through
immature and/ or tolerogenic dendritic cells as well as different types of
regulatory cells. Autoimmune diseases are associated with humoral or
cell-mediated immune reactions against one or more of the body?s own
constituents. Activation and clonal expansion of autoreactive lymhocytes is a
crucial step in the pathogenesis of autoimmune diseases. They result from the
complex interactions between genetic traits and environmental factors, among
which infections are the most likely cause. Several basic mechanisms may be
operating whereby an infectious agent actually induces apparent autoimmne
reactivity including molecular mimicry, bystander activation, induction of
costimulation, polyclonal activation, altered processing and expression of
cryptic antigens. Although many questions regarding autotolerance and etiop
athogenestis of autoimmunity have yet to be resolved, it is evident that
multiple overlapping pathways are operative in establishing, maintaining and
breaking autotolerance, as well as during the initiation, progression, and
final effector phases of autoimmunity.
Publisher
National Library of Serbia
Cited by
4 articles.
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