Immune System: the basics (with Video)

The immune system is a host defense system made up of many biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism’s own healthy tissue.  One of the recent key breakthroughs in medicine is based on a new understanding of the microbiota’s role in the body’s over-all defense system.


Pathogens, like cancer cells and lyme’s bacteria, can rapidly evolve and adapt, and thereby avoid detection and neutralization by the immune system. However, multiple defense mechanisms have also evolved to recognize and neutralize pathogens. Even simple unicellular organisms such as bacteria possess a rudimentary immune system in the form of enzymes that protect against bacteriophage infections. Other basic immune mechanisms evolved in ancient eukaryotes and remain in their modern descendants, such as plants and invertebrates. These mechanisms include phagocytosis, antimicrobial peptides called defensins, and the complement system.




1.  Beck G, Habitat GS (November 1996). “Immunity and the Invertebrates” (PDF). Scientific American. 275 (5): 60–66. Bibcode:1996SciAm.275e..60B. doi:10.1038/scientificamerican1196-60. Retrieved 1 January 2007.

2. O’Byrne KJ, Dalgleish AG (Aug 2001). “Chronic immune activation and inflammation as the cause of malignancy”. British Journal of Cancer. 85 (4): 473–83. doi:10.1054/bjoc.2001.1943.

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