Page 106 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

Innate immunity

Characteristics

➢ Exists at birth.

➢ Capable of a rapid response to microbes (Be the first

line of defense against infection).

➢ It exists naturally.

➢ Non–specific.

➢ No immune memory (innate immunity can’t be

enhanced by the second stimulation of the same

antigen).

First Line of Defense of innate immunity

A. Physical (Anatomical) barriers

1. Skin

• Intact skin affords high degree of protection against pathogens.

Thus, the skin acts as our first line of defense against invading

organisms.

2. Mucus membrane: secrete mucous in mouth respiratory tract, GIT,

and urinary tract, Mucous entrap pathogens and particles

3. Mucociliary clearance:

Continuous movement of the covering cilia helps to expel

microorganisms from the respiratory tract.

4. Nasal hair: traps microbes

5. Eye lashes and eyelids: prevent microbes and dusts from reaching the eye surface

General Microbiology & Immunology (PM 401) theoretical handbook Page 95