IMMUNITY

 IMMUNITY

The immune system is a system of biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue.

TYPES OF IMMUNITY

Immunity is divided into two divisions

1. Non – specific (innate immune system/inherent)
2. Specific/adaptive immunity which gives acquired immunity.

 

 NON SPECIFIC/NATIVE/INNATE

A portion of immunity resulting from general processes rather than processes directed at specific diseases or organisms.

 

This include resistance of skin to invasion by organisms, destruction by acid secretion by stomach and digestive enzymes organisms swallowed, phagocytosis of bacteria and other invader by leukocytes and cells of the tissue macrophage system.

 

SPECIFIC OR ADAPTIVE OR ACQUIRED

Acquired immunity is the type of immunity which has specificity against foreign substances.  Much of our immunity is caused by this system.This is acquired by previous experience of the organisms or its products.

TYPES OF AQUIRED IMMUNITY

1. NATURAL ACQUIRED IMMUNITY

This is passed from one generation to another though gene oar if one has suffered from a disease. It may be passive or active

Active:  antibodies are produced by the immune person.

Passive:  antibodies are produced elsewhere and are then given to the person.

A. NATURAL PASSIVE ACQUIRED IMMUNITY

Here the antibody is obtained by the young from the mother either across the placenta or in breast milk. The human placenta allows maternal antibody to pass into the foetal circulation.  The baby is then born having maternal antibodies against the diseases to which the mother is immune. This provides the baby with defence immediately after birth.  The antibodies do not persist. They disappear after a few months. Humans also obtain antibody in the breast milk. This is absorbed from the intestine and enters the circulation.

B. NUTURAL ACTIVE ACQUIRED IMMUNITY

Natural active acquired immunity: this is the type of immunity which is acquired in response to the entry of a live pathogen into the body (i.e., in response to an actual infection) - it has    long duration this applies to typhoid fever, measles and small pox.

 

2. ARTIFICIAL ACQUIRED IMMUNITY

This is also subdivided into active or passive according to whether the person actively participates by making his own antibodies (active) or only passively receives antibodies present in therapeutic sera.

A. ARTIFICIAL PASSIVE ACQUIRED IMMUNITY

In here the antibody is obtained or protection is derived from the infection (serum) of prepared or readymade antibodies. E.g. diphtheria, tetanus or gas gangrene.  (Antitoxic sera protection is received immediately but does not last long because infected serum with its antibodies fairly rapidly.

B. ARTIFICIAL ACTIVE AQUIRED IMMUNITY

This type of immunity develops as a result of vaccination with dead or attenuated pathogens or its toxins. The body is then able to produce its own antibodies against the pathogen.