Immunity

Definition

Ability of the body to resist all types of organisms or toxins that can damage tissues or organs.

TYPES

Specific or Acquired immunity
This develops after exposure to bacteria,viruses or toxins.
Innate or Non specific immunity
This type of immunity doesn’t require previous exposure to microorganisms or toxins.

COMPONENTS OF INNATE IMMUNITY


Neutrophils,Macrophages and Natural killer lymphocytes

Gastric acid

Intact skin and mucous membranes

Chemical compounds in blood and tissues


NEUTROPHILS

The neutrophils are mature cells that can attack and destroy bacteria even in the circulating blood.

MACROPHAGES

Begin life as monocytes in blood
Migrate to tissues to become tissue macrophages which can reach in size upto 80 microns.
Highly competant in combating infections

NATURAL KILLER CELLS

These are lymphocytes which can recognize and destroy foreign cells and even some infected cells.

GASTRIC ACID

HCL secreted in gastric juice by parietal cells destroy the microorganisms which are swallowed with food.

SKIN AND MUCOUS MEMBRANES

Intact healthy skin and mucous membrane act as efficient barriers against microorganisms.
PROTECTIVE CHEMICAL COMPOUNDS

These are
 Lysozyme ,a mucolytic polysaccharide that attacks bacteria and destroy them.
 Basic polypeptides, react with and inactivate certain types of Gram positive bacteria.

COMPLEMENT COMPLEX

A system of about 20 proteins that can be activated in various ways to destroy bacteria.

There are three complement pathways which the organism use as weapons to fight off pathogens,destroy tumors and kill viral infected cells .These are :

Lectin pathway
Alternative pathway
Classical pathway