Fundamentals of Microbiology

5.1.4 Immunity

Specific immunity – types

Acquired immunity:

It is a type of specific immunity a host develops after exposure to a suitable antigen or after transfer of antibodies or lymphocytes from immune donor

i. Naturally acquired active immunity

It is a type of naturally acquired immunity after an infection (disease) during normal activity. After the recovery from the disease, the person becomes immune to the disease. This immunity can be either life long or for only a few years.

ii. Naturally acquired passive immunity

This is an immunity acquired through transfer of antibody from one host to another for eg. Mother to fetus through placenta. It lasts only for a short time.

iii. Artificially acquired – active immunity

It is a type of immunity acquired through artificial means like vaccines. In this process, the host defence mechanism is induced to produce antibodies against the infectious agents.

iv. Artificially acquired – passive immunity

In this type of immunity, antibodies produced in vitro (outside the host body) are introduced into a host (to overcome a disease). For eg. Botulinum antitoxin is given to humans suffering from botulism food poisoning.

Humoral Immunity

The type of immunity that results from the presence of soluble antibodies in blood and lymph; also known as antibody-mediated immunity.

Cell – mediated immunity

The type of immunity that results from T-cells (T – lymphocytes) coming into close contact with foreign cells or infected cells to destroy them. It can be transferred to a non-immune individual by transfer of cells.