Types of Acquired Immunity: Active and Passive | Immunology

In this article we will discuss about the active and passive type of acquired immunity.

Type # 1. Active Immunity:

Adaptive immunity that is induced by natu­ral exposure to a pathogen or by vaccination.

It can be categorized into two types:

Naturally acquired active immunity:

Active immunity is acquired through conti­nuing, subclinical infections, caused by bacteria and viruses, which largely remain unnoticed and which is more advantageous than passive immu­nity.

Artificially acquired active immunity:

This type of immunity is usually obtained through vaccination or through administration of toxoids. Vaccines are killed or live attenuated microorganisms, whereas the toxoids are prepa­rations of toxins, which have been inactivated by certain clinical treatments or modifications so as to make them non-toxic in nature.

Type # 2. Passive Immunity:

Adaptive immunity is conferred by the trans­fer of immune products, such as antibody or sensitized T-cells, from an immune individual to non immune one.

It is of two types:

Naturally acquired passive immunity:

This can be acquired through trans-placental transfer of immunoglobulins (IgG) from mother to the foetus. This immunity lasts for about six months after birth. These antibodies of maternal origin protect the foetus and the infant from diptheria, streptococci, tetanus, rubella, mumps, and polio virus through passive immunity.

The secretory immunoglobulin (IgA) present in the mother’s milk provides local immunity in the gastrointestinal tract of the sucking infants. More­over human colostrums are rich in macrophages and lymphocytes (T-cells) which can survive in the intestine of the suckling infant for sometime, and thus can transfer cell mediated immunity.

Artificially acquired passive immunity:

It is achieved by administering specific anti­bodies or antiserum from one individual to another unimmunized individual, for a particular antigen. Routine passive immunization is done against different diseases like tetanus, botulinum, diptheria, hepatitis, measles and rabies. Antibodies against a microbe or its antigen or toxin can be raised in a suitable animal through repeated injec­tion of suitable antigen.