Immunity

Definitions:

    
Immunity is the relative ability of the body to resist almost all types of organism or toxins that tend to damage the tissues and organs.

  
 Immunity is also defined as the ability of the body to recognize, destroy and eliminate the antigenic material foreign to its own. It is normally a defensive mechanism of the body.

    
Antigen: An antigen is a substance which when introduced into the system is capable of including an immune response leading to the formation of antibody with which it reacts specifically.

     
Antibody: An antibody is a modified globulin (immunoglobulin) produced in response to an antigen with which it reacts specifically.

     
Immunization: It is a technique by which immunizing agents are introduced into the body for the production of antibody to prevent diseases.

  

    
Toxin: It is the product of bacterial metabolism and is toxic, i.e., inhibitory or lethal to the cells of the host.

   Toxin may be –

    (i) endotoxin

    (ii) exotoxin

  
 Toxoid: It is a derivative of the toxin which is devoid of toxigenicity but still possessing the antigenicity.

   Toxic are used for the purpose of immunization.

   Examples: Tetanus toxoids, diptheria toxoids.

Classification of immunity:

• Innate or nonspecific

Genetic

Mechanical

Humoral

Cellular

• Acquired or specific

a. Active

1. Natural
2. Artificial

b.Passive

1. Natural
2. Artificial