Sierra College Department of Biological Sciences

Discover the Biological Sciences

The introductory information for this site has been contributed as a joint assignment by students in Bio. Sci. 10.

Microbiology - Immunology

By: Ammon Danielson

1) Biological field or sub-topic chosen:


2) Define field or sub-topic:

Immunology is a field of science related an organism's defense system against hostile cells and microorganisms, or pathogens. As such, it is closely related to Pathology, with a focus on the defense, rather than the offense, of pathogens.

3) Describe in more detail the breath and depth of what could be studied or learned within this topic:

Immunology focuses on the immune system, and how it identifies and reacts to various diseases and physical disorders. In some cases, an organism is already resistant, which is called innate immunity. This immunity recognizes many pathogens automatically and destroys them before they can progress. To do this, it looks for general patterns that describe something as not being part of the host. However, the immunes system also heavily relies on adaptive immune response, which is how the organism reacts to a new antigen. An antigen, simply defined, is anything that stimulates the hosts specific immune response. Antigens can be very specific parts of a pathogen that the immune system uses to identify it as such. Once this occurs the blanket of immunity supplied by the innate immune system in effect spreads to cover the newly introduced pathogen. Immunology also examines immune system disorders, such as allergies and autoimmune diseases. An allergic reaction occurs when the immune system creates a defense against a substance that is normally not threating to the host. An autoimmune disease occurs when a host's own immune system attacks the host's cells to such an extent that a disease results.

4) Focusing on one major concept, principle, or group of organisms (as appropriate within the topic), describe its importance, relationships, functional aspects, or otherwise explain it in more depth as seems important to you and (potentially) the others in class:

Autoimmune problems can take many forms, and not all aspects of autoimmunity are necessarily detrimental. An autoimmune response can help a body fight tumors, and other possibilities are currently being researched. It is not currently know what causes many autoimmune disorders. There is however a strong genetic correlation for many autoimmune diseases, suggesting the the predisposition can be inherited. Some autoimmune problems can result from outside stimuli. For instance, when a human body creates antibodies to fight the bacteria which can lead to rheumatic fever, those same antibodies can attack tissues in muscles found in the heart. This is due to some similarities between those tissues and the bacteria the antibodies were originally produced to fight.

When classifying autoimmune diseases, they fall into two general categories; localized or organ-specific, and systemic. Organ-specific autoimmune diseases target particular areas of the body, while systemic autoimmune diseases can affect many parts. Actually placing a disease into one of these categories can be difficult however, because, as mentioned earlier, the origin is not always known. For this reason it could appear that an autoimmune disease targeting one organ actually affected the entire body simply because symptoms overlap. When an autoimmune response targets its own tissue, it can lead to inflammation and direct damage to the tissue.

There are three general ways that an autoimmune disease can be treated. The first, is with medication to reduce inflammation. Various treatments exist for rheumatoid arthritis to reduce the inflammation in joints that manifest after the immune system has attacked tissues there. Second, medication can be introduced which suppresses the immune system (immunosuppressive) and with it the autoimmune response. This can be effective is reducing the effect of lupus, and autoimmune disease that can attack many different organs in the human body. Finally, sometimes medication can compensate for the damage done. In the case of a type of Diabetes cause by an autoimmune response, insulin can be supplemented to compensate for what is no longer produced by the pancreas that was damaged.

5) In studying and discovering more about this topic, what was the most interesting aspect, fact or some other piece of information that you have learned.

The process that can lead to an autoimmune response as a result of infection. As mentioned in the definition, an antigen can identify a foreign substance as being harmful by analyzing only a very small part of its structure. The immune system does not necessarily look at a bacteria and realize that it, as a whole, is bad for the system. Instead, it recognizes that the particular bacteria has the equivalent of black hair. So it says to itself, "My body doesn't have black hair, this must be foreign. Kill it!" Unfortunately, as described in the case of rheumatic fever, this isn't always the case. Basically, some heart tissue might have the same hair color as a strain of bacteria.

6) References – provide references used and at least two Web sites with additional information on this topic (or sub-topic) for anyone that would like to learn more:

"Allergy." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online. 8 Sept. 2007 <>.
"Antigen." Medline Plus. 2007. A.D.A.M. Inc. 8 Sept 2007. <>
Baron, Samuel, ed. Medical Microbiology - 4th Edition. Galveston, TX: The University of Texas Medical Branch at Galveston, 1996.
Janeway, Charles, et al. Immunobiology: The Immune System in Health and Disease - 5th Edition. New York: Garland Publishing, 2001.
"Immunology." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online. 8 Sept. 2007 <>
"Tips to Remember: What is an allergic reaction?" AAAAI. 2007. American Academy of Allergy, Asthma and Immunology. 8 Sept 2007. <>

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