active and passive immunity

 Acquired Immunity

Acquired immunity is immunity acquired after birth or during the life time of an individual.

Acquired immunity is of two types;

1. Active immunity

2. Passive immunity

1. Active immunity

B-cells, T-cells, based on memory.

It develops after the entry of antigen in the body of an individual.

Immune system actively responds by producing specific antibodies.

Acquired Active immunity is of two types;

1. Natural acquired active immunity 

2. Artificial acquired active immunity

1. Natural acquired active immunity

It develops from exposure to an infectious agent.

This immunity develops when own cells of the person produce antibodies to antigen, when infection enters.

Remains active for longer period.

It takes a long time to develop immunity by the formation of antibodies.

2. Artificial acquired active immunity

It is acquired artificially by vaccination. Which is madeup of live, attenuated microorganisms or killed microorganism or toxoid from microorganisms or their antigens.

1. Bacterial Vaccine

a. Live;

BCG

Anthrax vaccine

Oral typhoid fever vaccine 

b. Killed

TAB for enteric fever

Cholera vaccine

Pertussis vaccine

2. Bacteria product

TT (tetanus toxoid)

DT (diphtheria toxoid)

Capsular polysaccharides of N. Meningitidis and H. influenzae (Type B)

3. Viral vaccines

a. Live

OPV for polio

MMR

Varicella

b. Killed

IPV (inactivated poliovirus vaccine)

Natural and non- neural rabies vaccine

Hepatitis A and B

Influenzae

2. Passive Immunity

It develops when readymade antibodies enter the host body through external source.

Passive immunity are two types;

1. Natural passive immunity

2. Artificial passive immunity

1. Natural passive immunity

Through placenta to child (IgG)

Through (IgA) breast milk to baby

Natural passive immunity is congenital immunity.

It develops fetus during pregnancy. IgG antibodies can cross the placenta barrier and enter in fetus through umbilical cord. 

After birth IgA antibodies are passed through first breast milk (colostrum) to child.

2. Artificial passive immunity

It is manmade. 

It is produced from injection of antibodies (antisera).

For example; tetanus, antitoxin, antivenom, TAB, Hepatitis

Artificial acquired passive immunity is induced by an injection of antibodies taken from the circulation of an animal or another person (serum).