Elements of Immunity

The term immunity is defined as the resistance shown by the host against the adverse effects caused by microbes and their toxic products. In vertebrates two types of defense mechanisms work together to contact infection.

1. Innate Immunity (or) Non-Specific resistance

2. Acquired immunity or Specific resistance

I) Innate Immunity:

a) It is a non-specific immunity.

b) This mechanism of immunity is similar for most types of infections, hence its name.

c) Its resistance to infection is by blocking the entry of pathogens into the body or by destroying the microbes through means other then antibodies.

d) Thus no-specific defense mechanism provides innate immunity which operates through many factors.

1) First line Defense (External Defense):

            First line defenses are physical barriers like SKIN, MUCUS MEMBRANE, Vaginal Bacterias

2) Second line Defense (Internal Defense):

            Second line defenses are Biochemical factors and Cellular factors

II) Acquired Immunity:

The resistance developed by man during his life is known as Acquired immunity or adaptive immunity. This is distinct from innate immunity in that it is due to specific antibodies or sensitized lymphocytes produces in response to specific antigens. Hence, this immunity is also known as specific immunity.

This acquired specific immunity is of two types namely Active and Passive.

Both active and passive immunity may be Natural or Artificial.

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