Question

What does the word “tolerance” mean in the context of immunity? What happens when tolerance fails?

Answer 1

Immunological tolerance describes a diverse range of host processes that prevent potentially harmful immune responses within that host.

This is achieved by avoidance of adaptive immunity, such as the forms of immune privilege seen in maternal acceptance of the fetus, in cancer, and in diverse body tissues; or through fine control of adaptive immunity in lymphocytes throughout their lifetime

An understanding of mechanisms underlying tolerance promises opportunities

.to therapeutically reprogram the immune system to treat autoimmune diseases and allergies,

.to ensure improved acceptance of transplants,

.to provide better vaccines against microbes and cancers.

Immune tolerance is achieved under conditions that suppress the immune reaction; it is not just the absence of an immune response. The latter is a process of unresponsiveness to a specific antigen to which a person is normally responsive.

Self-tolerance is the immune system's ability to recognize what is ‘self’ and not react against or attack it.

There is a central and peripheral tolerance of B or T cells.

Central tolerance of T cells, which makes the repertoire of T cells in the periphery non-responsive to self-antigens, is clonal deletion in the thymus (or negative selection).

If immunological self-tolerance is lost, the body develops an autoimmunity against its own tissues and cells, which become the source of the autoimmune disease.

Self-tolerance plays a key role in the prevention and treatment of immune disorder diseases, especially autoimmune diseases.

ie., immune response is generated against component or products of its own tissues treating them as foreign material and attacking them.

Eg

rheumatic arthritis,multiple sclerosis,type1 diabetes