This document discusses immunological tolerance and autotolerance. It defines immunological tolerance as antigen-specific unresponsiveness and distinguishes it from immunosuppression, which causes generalized depression of the immune response. Autotolerance is the inability to react against self. There are two types of tolerance - central and peripheral. Central tolerance involves clonal elimination of autoreactive lymphocytes in the thymus or establishment of low or high zone tolerance through continuous suboptimal or supraoptimal antigen exposure. Peripheral tolerance blocks existing effector immune responses through mechanisms like regulatory T cells or blocking antibodies.

1. Disorders of Immunity - 2
Immunological tolerance & Autotolerance
Dr.CSBR.Prasad, M.D.

2. Out come of an encounter with an antigenOut come of an encounter with an antigen
Hypersensitivity

3. Immunological toleranceImmunological tolerance
Definition:
Antigen specific immunological
unresponsiveness

5. Immunological toleranceImmunological tolerance
Tolerance Vs Immunosuppression:
Tolerance Immunosuppression
Ag specific (Response
to other Ags is normal)
Generalized depression
of immunological
response to all Ags

6. Immunological toleranceImmunological tolerance
Autotolerance
Central type Peripheral type
Interference 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

7. Immunological toleranceImmunological tolerance
Tolerance
Central type:Central type:
1.Clonal elimination
2.Low-zone / high zone tolerance
3.T-suppressor circuit

8. Immunological toleranceImmunological tolerance
Tolerance
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

9. Immunological toleranceImmunological tolerance
Tolerance
Central type:Central type: Low / high zone tolerance
Optimal dose for a response to occur
Continuous suboptimal dose results in the
development of tolerance – Low zone
Eg: Thyroxin, Thyroglobulin
Continuous supraoptimal dose also will
result in tolerance – High zone
Eg: Ig

10. Immunological toleranceImmunological tolerance
Tolerance
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

11. Immunological toleranceImmunological tolerance
Tolerance
Peripheral type:Peripheral type:
Blocking antibodies
-large quantities of abs
-different type of abs Eg: Br.asthma IgG

12. E N D