presentation5 innate immunity

7/28/2019 Presentation5 Innate Immunity

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INNATEIMMUNITY

Dr. A. A. Wegdan


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Immunity

The main function of the immune system is to

prevent or limit infections by microorganisms.

The immune response can be:

a. Innate (natural or nonspecific).

a. Adaptive (acquired or specific).


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Innate (Nonspecific) Immunity

It is naturally occurring.

Non specific and includes:

Natural barriers to infectious agents.

Humoral proteins.

Phagocytosis and natural killer cells.

Inflammation and a variety of other

nonspecific factors.


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Mechanisms Of Innate Immunity

1- Physiologic (Natural) Barriers at the Portal ofEntry.

2- Humoral Proteins.

3- Phagocytosis.

4- Reaction to Infection.


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1- Physiologic (Natural) Barriers at the

Portal of Entry1- Skin

a) Intact skin.

b) Fatty acids and lysozyme.

2- The Respiratory Tract

a) The hairs of the anterior nares.

b) Respiratory cilia.

c) Cough and sneezing reflexes.

d) Surface phagocytes.


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Portal of Entry3- The Conjunctiva

a) The blinking reflex.

b) The circulation of tears.

c) Lysozymes.

4- Gastrointestinal Tract

a) Normal flora of the buccal cavity and colon.

b) Low pH of the stomach.

c) The digestive enzymes.


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Portal of Entry.

5- Genital Tract

a) The thick stratified epithelium of adult vagina

b) Normal flora and low pH of the vagina.


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Portal of Entry.


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2- Humoral Proteins

If microorganisms succeed in overcomingthese natural barriers and be able to penetrate

inside the body, their growth will be limited by a

second strong line of defense:Humoral Proteins

The body's innate resistance to many pathogens

is provided by enzymes and other proteins in the

blood and tissue fluids.

These proteins are the effectors of humoral

innate immunity.


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2- Humoral Proteins

a) Lysozymes:digest the peptidoglycan ofbacterial cell wall.

b) Acute phase proteins e.g. C-reactive

protein, coagulation factors:participate inantimicrobial defense.

c) LPS-binding protein (LBP) and soluble

CD14:enhance phagocytosis.


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2- Humoral Proteins

d) Defensins:small peptides which can lysemicroorganisms directly.

e) Complement components (C3a, C5a):enhance the inflammatory response and

facilitate phagocytosis.

f) Interferons (alpha and beta): help control

of viral replication.


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3- Phagocytosis

A- Phagocytic Cells:

During bacterial infection, the number ofcirculating phagocytic cells often

increases. Types phagocytic cells:

1- Granulocytes (polymorphnuclear

leucocytes or neutrophils).


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3- Phagocytosis

2- Macrophages (circulating phagocytic

monocytes).

They are derived from monocyte stemcells in bone marrow and have a longer

life span than circulating neutrophils.

a) Blood monocytes.

b) Tissue macrophages; either wandering in

body spaces or fixed macrophages.


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3- Phagocytosis

Tissue macrophages


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Steps of Phagocytosis

a) Chemotaxis

The process by which

phagocytes are attracted

to the sites of

inflammation.

b) Ingestion (Engulfment)

Phagocytes engulf the

microorganism to form a

vacuole (phagosome).

c) Killing

1) Oxidative Mechanism.

2) Non-oxidative

Mechanism (lysosomes).


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Steps of Phagocytosis

c) Killing1) Oxidative Mechanism.

- Increased generation ofsuperoxide anions (O2).

- Increased release of H2O2.

- In the presence of oxidizingcofactors, acid pH and theenzyme myloperoxidase,H2O2 is converted tohypochlorite (HOCl) which is

an effective bactericidalagent.

2) Non-oxidative Mechanism(lysosomes).


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5- Reaction to Infection

1. Non specific reactions1. Inflammation:

Vasodilatation.

Oedema and swelling.

Migration of Polymorphonuclear cells.

2.Fever: The most frequent systemic manifestation.

Through the action of chemical stimuli on the

thermoregulatory center of the brain.a) Bacterial endotoxins.

b) Disintegrated leucocytes and tissue debris(endogenous pyrogens).


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5- Reaction to Infection

2. Specific reaction:

Through stimulation of the immunological

system.

Formation of specific antibodies and/or cell-mediated immunity.

This response helps in:

a) Recovery of the patient from the currentinfection.

b) Immunity against future re-infection.


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presentation5 innate immunity

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