What is Immunology

A very common question that what is immunology, so Immunology is the branch of biology which deals with the immune system and the immunity of the body.


Immunity is the resistance of the body against the infectious organisms. Any organism which causes a disease in the body is called pathogen. The individual person or animal infected by the infectious organism is called host of the pathogen. Not all the foreign organisms are pathogens, some of them are beneficial to the host.

For example:

Bacteria in the gut help in digestion of the food and also synthesize essential components, like vitamin K and vitamin B12, for their host. These organisms are called the commensals.

Common pathogens:

The most common organisms causing diseases are viruses, bacteria, fungi, protozones and helmens (worms).


Among the viruses, the most common pathogenic viruses are; hepadna virus, herpes virus, pox virus, picorno virus, myxo virus and retero virus.

The hepadna virus causes HBV.
The herpes virus causes chickenpox, it also causes genital organs effects loke blister appearance.
The pox virus causes small pox.
The picorno virus causes polio and common cold.
The myxo virus causes measles and mumps.
The retrovirus causes AIDs and HIV.


Among the bacteria, pathogenic bacteria are; clostridium, mycobacterium, vibrio, nesseria etc.

The streptococcus bacteria cause pneumonia.
The clostridium bacteria, clostridium tetinii cause tetanus, clostridium botulinum cause botulism, clostridium salmonella causes salmonellism.
The mycobacterium cause tuberculosis and leprosy.
The vibrio bacteria cause cholera.
The nesseria bacteria cause gonorehea, other diseases of genital organs and blindness in young children.


Among the fungi (yeast and molds), the most common infectious fungi include; cryptophytons, candida, cryptococcus.

The cryptophyton fungi cause ring worm diseases, athlete’s feet, jock itch (occurs in the growing regions).
The candida fungi cause thrush.
The cryptococcus fungi cause meningitis.


Among the protozoans, the common pathogens include; plasmodium, tripanosoma, giardia.

The plasmodium cause malaria.
The giardia cause giardiasis.
The tripanosoma cause chaga’s disease.


Among the helminthes, tacnia, schistosomes, ascaris, onchocera are the most common pathogen found.

The tacnia is responsible for pork worm and beef worm.
Schistostoma has 3 species and it causes schistostomiasis.
The ascaria causes ascariasis which spreads all over the body.
The onchocera causes river blindness. It is commonly called eye worm, black fly is its victor. Its larvae develops in the running water and then fly as an adult.

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