QS Study


A human body has the ability to resists almost all types of organism or toxins that tend to damage the tissue and organ. This capacity is called immunity. It is the capability of multicellular organisms to resist harmful microorganisms from entering it. Our immune system protects us and helps fight off disease. The healthy immune process is capable to recognize invading viruses, bacteria and also produce antibodies to destroy or disable them.

Types of Immunity:

Acquired immunity-

  • Immunity that develops against individual agents such as, Bacteria, viruses, toxins and even foreign tissue from other animals. It is that which develops antibodies after an attack of an infectious disease or by a pregnant mother passing through the placenta to a fetus or by vaccination.

Hormonal immunity

  • The body develops circulating antibodies, which are globulin molecules that are capable of attacking the invading agents.

Cell-mediated immunity

  • Immunity is achieved through the formation of a large number of activated lymphocytes that are specially designed for destroying the foreign agents.

Innate immunity

  • Immunity that develops from general processes rather than from process directed at specific disease organisms called innate immunity.
  • It is the normal resistance components such as intact skin, salivary enzymes, and neutrophils, natural killer cells, which afford an early reaction against infection that is present in an individual at birth prior to contact to a pathogen or antigen.

Beneficial example of immunity

  • Vaccination of clinical and subclinical infection.
  • When an individual suffers from measl, smallpox etc. gets lifelong immunity.

The harmful effect of immunity

(i) Hypersensitive reaction, e.g., Asthma, Rheumatic fever.

(ii) Autoimmune diseases, e.g., SLE, RA.