Running head: VIRUSES, FUNGI AND PARASITES

Unit 7 - Viruses, Fungi and Parasites

June Saxton

Kaplan University

HS320

Susan Galindo

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VIRUSES, FUNGI AND PARASITES

Unit 7 - Viruses, Fungi and Parasites

With so many pathogens around it is a miracle that our bodies don’t succumb to disease

more than they do (The Dana Foundation, 2013). The fact that they don’t is a testament to the

amazing design of our immune systems.

THE IMMUNE SYSTEMS ROLE IN DEFENSE DURING INFECTION

The immune system defends again infection in several ways these include sounding the

alarm, defense, elimination and protection and preventing further infection. The first line of

defense that the immune system employs is the innate immune system. The white blood cells

(phagocytes) are constantly moving through the body looking for invaders. Their job is to find

invaders and engulf and ingest them. They also send a chemical alarm to the adaptive immune

system which brings more specialized cells into the battle. Dendritic cells identify the invader,

lymphocytes adapt and adjust to fight the specific threat. Lymphocytes consist of B and T cells.

The B cells can respond and fight invaders without any assistance, but in order for T cells to

respond they must receive a second danger signal from MHC molecules. It may take some time

for the T cells to get the message, but they are capable of learning from each repeated exposure

and respond quicker each time (The Dana Foundation, 2013).

The next phase of the fight is elimination. This phase uses the unique characteristics of

the phagocytes to engulf and ingest invades, the killer characteristic of the T cells and the B cells

ability to fight the invaders eliminate the treat (The Dana Foundation, 2013).

The final phase of the fight is recovery. After the fight is over the phagocytes and

lymphocytes retreat, the inflammation subsides and symptoms gradually disappear. However, the

B and T cells retain the memory of how to fight the invader if it returns (The Dana Foundation,

2013).

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VIRUSES, FUNGI AND PARASITES

PARASITIC AND FUNGAL INFECTIONS

Although both fungi and parasites are classified as eukaryotes there are two very different

organisms. Although fungi look more like plants than eukaryotes, they do not contain

chlorophyll, contain a carbohydrate (chitin) cells walls instead of cellulose, are not multicellular

like plants, they cannot synthesize their own food like plants but must rely on a more complex

organism for it (Pommerville, 2011). Parasites on the other hand are single-celled protozoa or

multi-celled animals such as parasitic worms (The Dana Foundation, 2013). Most fungi can be

transmitted directly from infected soil, air, water and plants while parasites can infect humans

either directly from contaminated water or food or through an arthropod that has been infected

(Pommerville, 2011).

HOW THE IMMUNE SYSTEM CHANGES IN IMMUNOCROMPROMISED PERSONS

Even with all the weapons that the immune system has the immune system sometimes

microbes manage to outsmart it or elude detection. This especially is true if the immune system

is compromised in any way. This can happen due to medical conditions or treatments or

environmental toxins that suppress our immune systems because the system is so complex and

relies on specialized cells any breakdown in the system can render the whole system inadequate.

The effectiveness of the whole system depends on the ability of each component to fulfill its

role. Also because microbes evolve rapidly and humans don’t, they have the advantage over our

immune systems especially if it is not functioning properly (The Dana Foundation, 2013).

A healthy immune system is the best defense against all types of microbial infections, but

failing that it is important to know what treatments work best against each of the four categories

of harmful microbes i.e. bacteria, viruses, fungi and parasites.

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VIRUSES, FUNGI AND PARASITES

References

The Dana Foundation. (2013). The immune system’s role in protection. Retrieved from

http://www.dana.org/news/publications/detail.aspx?id=4274

Pommerville, J. (2011). Alcamo's fundamentals of microbiology. (9 ed., Vol. 9).

Sudbury: Jones & Bartlett Publishers.

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