U4 AOS1 Topic 1: First Line of Defense

The immune system can be innate and adaptive. The innate immune system has non-specific response against pathogens whereas adaptive immune system has specific response to pathogens.  The first line of defense is a component of the innate immune system i.e. non-specific defense system which involves physical and chemical barriers against pathogens.

Barriers in plants:

Plants have defense mechanisms to cope with pathogens.

·        The physical barriers in plants include thick bark, waxy cuticle, thorns and trichomes.

·        The chemical barriers include production of certain chemicals to repel or kill pathogens for example saponins, defensins, phenols and chitinases which have anti-microbial properties.

Barriers in animals:

·        Physical barriers in animals include intact skin, cilia and mucous secretion.

·        Chemical barriers include acidic sweat, stomach acid, digestive enzymes, low pH in vagina and antibacterial proteins in semen

·        Microbiological barriers include normal flora i.e. non-pathogenic bacteria on skin, digestive tract and vagina.