IMMUNITY

IMMUNITY

"A state of being protected against microbial invaders by cirtue of being able to resist and/ or overcome harmful effects of these invaders."

There are two types of immunity

1. humoral immunity
2. cellular immunity

1.Humoral Immunity

• dependent upon B.lymphocytes
• Effective against bacteria and virus

2.Cellular Immunity

• Dependent upon T.Lymphocytes , which liberate chemical , called lymphokines.
• Effective against intracellular viruses fungi , protozoa , helminthes , transplanted tissue and cancer cells.

Kings of Immunity

There are two kinds of immunity.

1. Innate / inborn immunity ( non specific immunity )
2. Acquired Immunity ( specific immunity )

1. INNATE / INBORN ( NON SPECIFIC IMMUNITY )
• It is also known as native or natural immunity.
• Constitutive for species i.e present at birth.
• Does not result from previous contacts with antigenic elements.

It can be subdivided into 2 defense lines.

1.      first line of defense

2.      second line of defense

1. First line of Defense is a surface protection composed of anatomical and physiological barriers that keep microbes from penetrating sterile body compartments.

These barriers are as follow

1.      Physical barrier  ( Skin and mucous Membranes )

2.      Chemical Barrier ( secretions of sebaceous glands , sweat glands , lysozyme & various gastric secretions )

3.      Genetic Barrier

2. Second line of defense is a cellular and chemical system that comes immediately into play if infectious agents make it past the surface defenses e.g

1.Inflammation

2. Phagocytosis

3. Interferon

4. Complement

3. ACQUIRED IMMUNITY ( SPECIFIC IMMUNITY )

               ( THIRD LINE OF DEFENSE )

It refers to the resistance against infectious agents obtained during life. It may be either humoral or cellular in nature.

There are four types of acquired immunity.

1. naturally acquired active immunity
2. naturally acquired passive immunity
3. artificially acquired active immunity
4. artificially acquired passive immunity

1. Naturally Acquired Active Immunity

Developed in a person when he comes in contact with antigen in his environment by natural process.

EXAMPLE : Clinical , subclinical , asymptomatic infection

2. Naturally Acquired Passive Immunity

Developed in a person when he receives pre-made antibodies through natural routes such as IgG antibodies of mother may cross the placenta to enter into the fetus.

EXAMPLE : mother's antibodies transferred to fetus

3. Artificially Acquired Active Immunity

It Is acquired when an individual is vaccinated

EXAMPLE : Vaccination

4. Artificially Acquired Passive Immunity

It results when an individual receives an injection of humoral antibody formed by some other person.

EXAMPLE : Injfection of specific antibodies ( Anti-tetanus Antibodies )