aquired immunity

8/2/2019 Aquired Immunity

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AQUIRED IMMUNITY

(Adaptive or Specific)

Husan BanoAssociate professor

Department PhysiologyAl-Tibri Medical College


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REVIEW OF PREVIOUSLECTURE


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As microorganism enter into

body our first line of defenseactivated.


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First line of defense

(Innate Immune)

Body uses physical and chemical barriersagainst infection such as:

Skin prevent entry of microorganism. Sweat Itschemicals kills pathogens.

Tears - have lysozyme which digest forigen

body. Saliva also has lysozyme. Mucus - trap pathogens. Stomach Acid destroys pathogens


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Second Line of Defense(Innate Immune)

If first line of defense is weak, thepathogen enter into the body and an

infection starts.

Now the bodys second line of defenseactivated. This is called an Inflammatoryresponse.


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Inflammatory response.

Redness - due to capillary dilation andincreased blood flow .

Heat - due to capillary dilation resulting inincreased blood flow

Swellingdue to flow of plasma into the

damaged tissue

Pain due to tissue destruction .


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Third Line of Defense

(Acquired immunity)

If the second line of defense is not enough

the body's Third-Line Defenseor immunesystem activated.

The immunity which is caused by immunesystem is called Acquired immunity


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Acquired immunity

Acquired immunityare of 2 types:

1. Cell mediated immunity or T-cell immunity

2. Humoral Immunity or B- cell immunity


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Acquired Immunity

Lymphocytes play an important role inacquired immunity. (Both cell mediated andhumoral type).

Lymphocytes formed from bone marrow fromstem cell. These are called BasicLymphocytes.

They mainly located in lymph nodes.


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Acquired Immunity Cont.

Besides bone marrow, They are alsoformed from lymphoid organs.

In lymphoid tissue, the lymphocytes aremainly of two types.

1. T- lymphocytes2. B- lymphocytes


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Those basic lymphocytes which enter into

thymus for preprocessingor activation, calledT- Lymphocytes.

These are responsible for Cell-mediatedimmunity.


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On the other hand, those basiclymphocytes which enter into liver for

activation in foetal life or other bursalequivalent organ in adult life, are called

B- lymphocytes

These are responsible for Humoralimmunity.


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1. Cell mediated or T-cell immunity.

It is mediated by T-lymphocytes

T-lymphocytes recognize foreign body bymeans of surface receptors

T-lymphocytes attack and destroy foreignmaterial directly or through release of

soluble mediators i.e. cytokines


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T-cells Ag Macrophageconverted into

lymphoblast

converted intoTremendous activated T cells memory cells

Lymphoid organs

Via lymph enter into circulation

Activated T- cellcirculation

Cytotoxic

T- cell

Supressor

cells

Helper

T-cell

DestructionOf

Antigens

Causes Directly

ActivationOf

OtherImmune response

Secretes

lymphokinaseA


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2. Humoral immunity Or(B- cell immunity)

B-lymphocytesare responsible forhumoral immunity.

B- lymphocytes produces Plasma Cells.

Plasma cells produced antibodies.

These have the ability to recognize andbind to antigen.


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Humoral immunity Or(B- cell immunity)

B- lymphocytes first discover in bird in anorgan called Bursa fibricus.( This is the

lymphoid organ associated with GIT.

In human being several bursal equivalent

organs are present such as spleen ,lymphnode, tonsil etc.


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Mechanism Of Humoral orB- cell immunity:

Stem cellB- lymphocytesBone Marrow

Basic lymphocytesCirculation

Activation, maturation of B-lymphocytesBursal equivalent

organs

Release B- lymphocytesCirculation

Goes to areas of B-cell in lymphoid organsLymph node

Spleen


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Lymph node B- cell areas

( B- lymphocytes)

Plasma blasts

Lymph nodeSpleen

Plasma cells

Anti bodies

Memorycells


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Ab + Ag complex

neutrilization Opsonization Complement activation Destroy antigen


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Active Immunity

Active immunity occurs when one makeshis/her own antibodies.

This type of immunity is long term.


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Passive Immunity

Passive immunity occurs when theantibodies come from some other source.

This type of immunity is short term. e.g

breast milk by whichbaby gain passiveimmunity


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Vaccination:

A vaccination is an injection of a weakestform of the actual antigen that causes the

disease.

The injection is so weak that person notbecome sick, but his B lymphocytes will

recognize the antigen, and produceMEMORY cells for long term immunity


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aquired immunity

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