2 immunology-csbrp

Disorders of Immunity - 2Immunological tolerance & Autotolerance

Dr.CSBR.Prasad, M.D.

Out come of an encounter with an antigenOut come of an encounter with an antigen

Hypersensitivity

Immunological toleranceImmunological tolerance

Definition:

Antigen specific immunological unresponsiveness

Immunological toleranceImmunological toleranceTolerance Vs Immunosuppression:

Tolerance ImmunosuppressionAg specific (Response to other Ags is normal)

Generalized depression of immunological response to all Ags

Immunological toleranceImmunological toleranceAutotolerance

Central type Peripheral typeInterference at recognition phase

Blocking the already existing effector mechanism

DefDef: Inability to react against self: Inability to react against self

TypesTypes: Two types: Two types

Immunological toleranceImmunological toleranceTolerance

Central type:Central type:

1.Clonal elimination2.Low-zone / high zone tolerance3.T-suppressor circuit


Central type: Central type: Clonal elimination

Complete absence of production of lymphocyte clones with Ag-specific receptors

Eg: AutotoleranceEg: Autotolerance

Continuous exposure to Ag is necessary to maintain such tolerance


Central type: Central type: Low / high zone tolerance

Optimal dose for a response to occurContinuous suboptimal dose results in the

development of tolerance – Low zone Eg: Thyroxin, ThyroglobulinContinuous supraoptimal dose also will

result in tolerance – High zone Eg: Ig


Central type: Central type: T-suppressor circuit

Improtant physiological function of Ts cells is to establish tolerance

Suboptimal response of Ts is responsible for many autoimmune diseases

With aging Ts cell number drops, hence circulating autoantibodies are more frequently seen in elderly


Peripheral type: Peripheral type:

Blocking antibodies-large quantities of abs-different type of abs Eg: Br.asthma IgG

2 immunology-csbrp

Health & Medicine