Immunology and Human Disease Flashcards
Why does the human body make a great host?
The human body makes a great host since it provides optimal temperatures, nourishment, and protection.
What is the estimated number of bacteria species?
There are currently an estimated 10 million to a billion different species of bacteria. To make things even more complicated, there are different serotypes of species.
What are serotypes?
Serotypes are distinct antigenic variations that exist between bacteria of the same species.
Name an example of a bacteria with many serotypes. What does this mean for our immune response?
For example: there are an estimated 92 different serotypes of Streptococcus pneumonia. Therefore, there are different antigenic macromolecules (epitopes) present on the capsular surface of different strains of S. pneumonia. An individual can be infected and successfully remove one serotype of S. pneumonia, but be incapable of removing a different serotype because immunological memory would not recognize it.
What is antigenic drift?
Antigenic drift is defined as point mutation in genes causing alterations in the structure of an organism. For example: yearly influenza outbreaks. The influenza bug changes from year to year, and this is why the flu shot has to be administered yearly. The result of antigen drift within the community is an epidemic, a localized outbreak resulting in mild disease.
What is antigenic shift?
Comparatively, antigenic shift is defined as radical changes in surface antigens based on reassortments of the organisms genome. This is often the case in pandemics, which result in severe disease states and increased mortality on a global scale. For example: the Bubonic Plague.
What are virulence factors?
Virulence factors are molecules secreted or expressed by pathogens that enable them to colonize, divide, and cause damage.
Name some examples of toxin virulence factors, pathogen example and associated disease state.
- Neurotoxin, cytotoxin, and enterotoxin that destroys host cells.
- Pathogen: Escherichia coli.
- Disease state: Enterohemorrhagic E. coli (EHEC).
What pathogen uses its capsule as a virulence factor? What benefit does it give the pathogen?
Streptococcus pneumonia uses its capsule as resistances to phagocytosis. Pneumonia.
What is the virulence factor whose function is to non-specifically bind to MHC class II molecules and cause the widespread activation of T Cells?
Superantigens E.g. Staphylococcus aureus that results in Toxic Shock Syndrome
What virulence factor and pathogen that results in the disease state Toxoplasmosis?
Vesicle Formation - Creates its own membrane enclosed vesicle within the cell, so MHC is unable to bind and present peptides. Toxoplasma gondii uses this to cause Toxoplasmosis.
What virulence factor destroys polysaccharides that holds cells together?
Enzymes (ex. Hyaluronidase) - Destroys polysaccharide that holds cells together so that the pathogen can spread through human tissue easier. Streptococcus pyogenes uses this to cause Necrotizing fasciitis.
What is latency?
Latency occurs when a pathogen enters a dormant state. The organism has entered cells and is therefore present, but is not undergoing replication, so no disease state is apparent.
Give an example of an organism that is capable of latency?
An example of an organism that is capable of latency is herpes simplex virus 1, which is the causative agent in cold sores. During the primary infection herpes simplex virus 1 will result in an infection. When the immune system subsides the virus will go dormant within the trigeminal ganglion (which is not infiltrated by immune system cells). Once the immune system is compromised (colds, stress, flu, etc.), the virus will re-emerge.
Describe the HIV virus.
HIV, Human Immunodeficiency Virus, is an infectious agent that targets cells of the immune system. HIV is an enveloped virus that contains an RNA genome, reverse transcriptase, integrase, protease, and glycoproteins (gp41 and gp120).
How does HIV infect its host?
Gp120 on the HIV surface recognizes CD4 on the T cell surface. Gp41 then mediates fusion between the virus and the CD4 positive host cell. At this point, the RNA genome is introduced, and reverse transcription transcribes the viral RNA into cDNA (complementary DNA). The cDNA is incorporated by integrase into the helper T cells DNA genome. When the T cells normal transcription and translation process takes place, viral proteins are created. These are folded by protease and are delivered to the T cell surface where it forms a virus. The newly formed virus will then infect other neighboring T cells
What is the initial response of someone who contracts HIV?
When an individual is initially infected with HIV they exhibit flu-like symptoms. At first the immune system will respond to the viral invasion and anti-HIV is formed (antibodies to HIV).
What is seroconversion?
A detectable level of anti-HIV is referred to as seroconversion.
How does HIV evade the immune system if the person has anti-HIV?
The viral load will decrease, however, some of the virus remains within the T cells. When the immune system response subsides, the virus will slowly replicate until the viral load increases again. The T cell population will gradually decrease as the virus is increasing in numbers. This is referred to as clinical latency. T cells and viral numbers remain relatively constant and the individual is asymptomatic. Reverse transcriptase is a faulty enzyme that lacks proofreading capabilities. This means that as the HIV genome is reverse transcribed into cDNA there are inherent errors made, mutations. Therefore, HIV is highly mutable. As it increases in numbers it also mutates, which allows it to evade the host immune response.
When is AIDS officially diagnosed in a person with HIV?
When Helper T cell numbers are dwindling to very low levels. This stage is referred to as clinical AIDS, Acquired Immunodeficiency Syndrome. The immune system is incredibly compromised and the individual is extremely susceptible to opportunistic infections.
How many people have HIV and have died of AIDS according to the World Health Organization?
According to the World Health Organization there are approximately 34 million people living with HIV and approximately 35 million people that have died of AIDS (about the population of all of Canada).
Does genetics play a key role in a fully functioning immune system?
IR gene –> Stronger immune system with the gene.
Immunodeficiencies –> Can be genetically passed down from generation to generation resulting in individuals more susceptible to frequent and recurrent infections.
Describe the difference inheritance patterns that immunodeficiency diseases can be passed on by.
Immunodeficiency diseases follow predictable inheritance patterns. They can be dominant, recessive, or sex-linked. A) Dominant inheritance refers to the phenotypic expression of a trait when only one defective gene is inherited. B) Recessive inheritance requires two defective genes be inherited, one from each parent. If only one gene is inherited then the individual is an unaffected carrier. C) Finally, sex-linked inheritance refers to genes that are inherited on the X chromosome. Therefore, males are affected and females are often carriers.
What is the result if you have complement deficiency?
Deficiency in one or more of the complement proteins. Susceptible to frequent and persistent infections
What occurs if neutrophils and macrophages are unable to “stick” to epithelium to get to the site of infection?
Susceptible to frequent and persistent infections. E.g. Leukocyte Adhesion Deficiency
What if your body lacks receptors for IL-2, IL-4, IL-7, and IL-9?
Severe Combined Immunodeficiency (SCID): Susceptible to frequent and persistent infections.
Common Gamma Chain Impairment to make cytokine receptors for IL-2, IL-4, IL-7, and IL-9.
What occurs in ‘Wiskott Alrich’ and ‘Bare Lymphocyte’ conditions?
Wiskott Alrich: Impairment of platelets and lymphocytes Bare Lymphocyte: Lack HLA class II molecules Both cause severe combined immunodeficiency (SCID): Susceptible to frequent and persistent infections
What are environmental factors that affect your immune system? Name examples.
Environmental factors are all of the other elements that contribute to an individual’s immune status which are not inherited. These factors include chemicals that an individual might encounter, ionizing radiation, UV radiation, secondary effects of a chronic disease state (such as Diabetes Mellitus) that influences a component of the immune system, infections, trauma, smoking, exercise, aging, pregnancy, stress, and diet/malnutrition.
What is a hypersensitivity reaction?
Hypersensitivity reactions are defined as the adaptive immune response to innocuous molecules. Hypersensitivity is often used synonymously with “allergic reactions”. Note: However, there are different mechanisms that result in hypersensitivity reactions that are more complicated than just “allergies”.
Give an example of a hypersensitive reaction.
The immune system is sensitive to molecules that it should not usually respond to. For example: an individual may have a reaction to cat dander. The body should typically ignore this as it is a molecule that will not cause harm to the body. The body is hypersensitive, so it attempts to remove an infection that does not exist. An individual whose body responds to the cat dander will often have breathing difficulty, itchy eyes, and a runny nose as a result of histamine being released.
Why is there lower concentrations of IgE, eosinophils and basophils found in circulation?
IgE, eosinophils, and basophils are found in low concentrations within circulation, therefore there are less molecules/cells that can be activated to innocuous substances.
reactions, examples, and the hygiene hypothesis.
