unit 8 seminar immunology. the human immune system made up of 2 branches that work together:...

Unit 8 Seminar

Immunology

The human immune systemMade up of 2 branches that work together:

1.Innate (nonspecific) immune systemFirst and second line of defense

2. Acquired (specific) immune systemB and T cells

The two branches work together to fight infectious agents

Chemically controlled

innate (nonspecific)immunity

First and second line of defense

Innate immunity- first line of defense

• Intact skin

• Mucous membranes

• Normal microbiota

Innate immunity- second line of defense

• (phagocytic) white blood cells

• Inflammation

• Fever

• Complement

White Blood Cells (leukocytes)

• Neutrophils: Phagocytic• Basophils: Produce histamine• Eosinophils: Toxic to parasites, some phagocytosis• Dendritic cells: Initiate adaptive immune response, phagocytic• Monocytes: Phagocytic as mature macrophages

– Fixed macrophages in lungs, liver, bronchi– Wandering macrophages roam tissues

• Lymphocytes: Involved in specific immunity. B and T cells.

Phagocytosis of E.coli pseudopods

of macrophage entrap E.coli bacteria

bacteria brought into macrophage for destruction

inflammation

fever

• Increases metabolic processes in the human body

• Enhances inflammation, helps move WBCs

• Some infectious agents induce fever

The Complement System• Serum proteins

activated in a cascade

• Activated via one of three pathways

• Activated Complement proteins trigger 3 primary immune responses

Figure 16.10

1.

2.

3.

• The complement system is an important part of the innate immune system that has far-reaching effects on the body’s ability to fight off infection. Many pathogens have the ability to affect or disable individual proteins within the Complement system. In your opinion, which Complement protein (C5a? C1?) would be most devastating to the host immune system if it were to be inactivated by a particular pathogen? Why?

Acquired (specific)immunity

B cells and T cells

B cell immunity (humoral immunity)

• Bone marrow gives rise to B cells

• Some B cells (plasma cells) produce antibodies

• Other B cells become long-lived memory cells

• B cells primarily react to extracellular pathogens

T Cell immunity (cellular immunity)

• T cells primarily respond to intracellular Ags• Differentiate in the thymus, then migrate to

lymphoid tissue• Helper T Cells (CD4, TH)– TH1 Activate cytotoxic T cells

– TH2 Activate B cells to produce antibodies

• Cytotoxic T Cells (CD8, TC)– Destroy target cells with perforin

– Some T cells become long-lived memory cells

Other immune components

• Cytokines

• Chemokines

• Other chemical messengers

• As you have learned in this unit, the immune system does an exceptional job in clearing infections from the host. However, on occasion the immune system can actually make an illness worse by overreacting to a potential pathogen. One example is a phenomenon called “cytokine storm”. This occurrence takes place when the body is infected by specific pathogens. Some examples include the influenza virus that caused the 1918 Spanish Flu epidemic and more recently the SARS epidemic in 2003. What occurs during “cytokine storm” and how does it affect the host? Find an example of a more recent disease (hint: look at the flu virus) that induces cytokine storm.

Cytokine storm & Avian Flu

• “Acute respiratory viral infection (especially from the H5N1 subtype influenza virus) results in a cytokine storm effecting the lungs, and subsequent damage to alveoli and lung tissue results in the lethality seen in more severe flu viral infections, especially those fatalities among young healthy adults”

http://www.cytokinestorm.com/ accessed July 21, 2011

• Human society has evolved significantly over the past few decades. Populations of humans used to inhabit wide-open spaces and rarely had contact with large crowds of people. However, modern society requires people to live in very tight quarters and come into contact with possibly hundreds or thousands of people in a single day. Consider cities like New York City and Tokyo, Japan. Occupants in these cities are packed in tightly into subway systems and overcrowded conditions. When people in Japan are ill, they wear face masks to protect others, while in New York City this is not done. What are some other ways that people in these cities (and other large cities around the world) deal with potential exposure to pathogens?

Unit 8 Assignment

Unit 8 assignment: Microbial evasion of host immune defenses

Microbiology encompasses many aspects of pathogens and human reactions to infections. This project will allow you to trace pathogens through the infection cycle and human response to the infection.

Project requirements: Refer to Table 1.1 and answer the following questions for EACH organism listed above. Word requirements are outlined for each question - this represents a minimum number of words required. For each question answer in full and complete sentences, and provide both examples and scientific evidence to support your answer. Be sure to include a well-developed introduction and conclusion in your paper.

You may use outside sources, but the reading material for Units 7 and 8 should provide the majority of information you will need to complete the assignment. Be sure to include all references in APA format.

Table 1.1Organism Strategy to avoid host

immune systemCommon disease

Trypanosoma cruzi Changes surface antigens to avoid immune system

detection

American trypanosomiasis

Human immunodeficiency virus (HIV)

Virus infects and hides in macrophages and CD4 T-

cells.

Acquired immunodeficiency syndrome (AIDS)

Streptococcus pneumoniae Produce M proteins to inhibit phagocytes from

attaching

Pneumonia

Questions:

1. Give a brief overview of the disease including signs and symptoms. Who is typically affected by this infection?(Children? Immunocompromised patients?)? What is the pathogens’ portal of entry and exit? (100 word minimum)

2. How would the innate immune system react to this pathogen? Which components would react? (75 word minimum)

3. Would this pathogen primarily stimulate cell-mediated immunity or antibody-mediated immunity (T cells or B cells?) Why? (75 word minimum)

4. All of the organisms listed above have the ability to evade the host immune system, at least temporarily. Review Table 1.1 for the pathogens’ strategies used to avoid the host’s immune system. Why is this particular strategy helpful to the pathogen? How would this impact the pathogens’ ability to cause infection? How would the immune system compensate? (200 word minimum)

To access an archived seminar consult the Flex Seminar guide in Doc Sharing-

step by step instructions provided

Questions??

References

• Tortora, G., Funke, B., & Case, C. (2007). Microbiology: An Introduction (8th ed.). San Francisco, CA: Pearson.