What Is Meant By Immunological Tolerance?


Immunological Tolerance

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.

How can self tolerance be established?

Tolerance to self is a normal state that is maintained chiefly by clonal deletion of developing T and B cells and clonal deletion or inactivation of mature peripheral T and B cells.

What is tolerance in microbiology?

Introduction. Tolerance refers to the specific immunological non-reactivity to an antigen resulting from a previous exposure to the same antigen. While the most important form of tolerance is non-reactivity to self antigens, it is possible to induce tolerance to non-self antigens.

Is Immune Tolerance good or bad?

Immune tolerance is important for normal physiology. Central tolerance is the main way the immune system learns to discriminate self from non-self. Peripheral tolerance is key to preventing over-reactivity of the immune system to various environmental entities (allergens, gut microbes, etc.).

What are the organs of immune system?

Primary lymphoid organs: These organs include the bone marrow and the thymus. They create special immune system cells called lymphocytes. Secondary lymphoid organs: These organs include the lymph nodes, the spleen, the tonsils and certain tissue in various mucous membrane layers in the body (for instance in the bowel).

What are possible causes for a lack of self-tolerance?

Some pathogenic states in which autoimmunity has been implicated include: idiotype cross-reactivity, epitope drift, and aberrant BCR-mediated feedback. Self-tolerance errors result in autoimmune disorders such as celiac disease, type-1 diabetes, inflammatory bowel disease (IBD), multiple sclerosis to name a few.

What causes loss of self-tolerance?

Some common mechanisms for losing self-tolerance include reduced deletion or enhanced activation of autoreactive CD4+ T-helper (Th) lymphocytes, defective immunomodulation by CD4+ regulatory (Treg) and CD8+ suppressor (Ts) T-lymphocytes, dysregulated signaling (leading to a relative increase in pro-inflammatory …

What happens when self-tolerance fails?

The ability to discriminate between self and nonself antigens is vital to the functioning of the immune system as a specific defense against invading microorganisms. Failure of the immune system to “tolerate” self tissues can result in pathological autoimmune states leading to debilitating illness and sometimes death.

How does B cell tolerance develop?

Tolerance is regulated at the stage of immature B cell development (central tolerance) by clonal deletion, involving apoptosis, and by receptor editing, which reprogrammes the specificity of B cells through secondary recombination of antibody genes.

How do autoimmune diseases break tolerance?

Environmental triggers seem to play large roles in autoimmune responses. One explanation for the breakdown of tolerance is that, after certain bacterial infections, an immune response to a component of the bacterium cross-reacts with a self-antigen.

What are the two most common applications of cytokine therapies?


Because of their immunomodulatory, anti-viral and anti-proliferative properties, cytokines—principally interferon (IFN)-alpha and interleukin (IL)-2—are currently used for the treatment of immune-mediated medical illnesses, including cancer and viral infections (e.g., chronic hepatitis C, AIDS).


What is self antigen?

Medical Definition of self-antigen

: any molecule or chemical group of an organism which acts as an antigen in inducing antibody formation in another organism but to which the healthy immune system of the parent organism is tolerant.

Is passive immunity permanent?

However, passive immunity lasts only for a few weeks or months. Only active immunity is long-lasting.

How is tolerance achieved?

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.

Why do T cells become anergic?

T-cell anergy can arise when the T-cell does not receive appropriate co-stimulation in the presence of specific antigen recognition.

What is it called when your immune system begins to target its own cells for destruction?

An autoimmune disorder occurs when the body’s immune system attacks and destroys healthy body tissue by mistake.

Why are mature cells self tolerant?

Central tolerance is essential to proper immune cell functioning because it helps ensure that mature B cells and T cells do not recognize self-antigens as foreign microbes. … Due to the nature of a random receptor recombination, there will be some BCRs and TCRs produced that recognize self antigens as foreign.

Is clonal anergy reversible?

Clonal anergy is another mechanism of peripheral tolerance to self-antigens. In the context of oral tolerance, its involvement was first demonstrated based on a study that showed T cell tolerance could be reversed in vitro by exogenous IL-2 (Whitacre et al., 1991).

What is CTL cell?

CD8+ (cytotoxic) T cells, like CD4+ Helper T cells, are generated in the thymus and express the T-cell receptor. … CD8+ T cells (often called cytotoxic T lymphocytes, or CTLs) are very important for immune defence against intracellular pathogens, including viruses and bacteria, and for tumour surveillance.

What is self tolerance psychology?

Self-tolerance, on the other hand, acknowledges that we are not happy with ourselves yet urges us to learn to tolerate our inevitable mistakes and foibles. This for many is much more manageable. So try it next time! When you find yourself indulging in self- flagellation, think about being a little kinder to yourself.

What are the 4 types of immunity?

Humans have three types of immunity — innate, adaptive, and passive:

  • Innate immunity: Everyone is born with innate (or natural) immunity, a type of general protection. …
  • Adaptive immunity: Adaptive (or active) immunity develops throughout our lives.

What are the 4 main organs in the immune system?

The key primary lymphoid organs of the immune system are the thymus and bone marrow, and secondary lymphatic tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, and skin and liver.

What is the largest immune organ?

The spleen is the largest internal organ of the immune system, and as such, it contains a large number of immune system cells.