Lecture 1: Intro Flashcards
1. Concept of immune responses through the history of vaccination 2. Routes of infection and barriers to infection-resistance 3. An overview of innate and adaptive immunity
4 General Types of Pathogens
- Virus (ex: Rotavirus)
- Fungus (ex: Candida albicans)
- Parasite (ex: Filaria)
- Bacterium (ex: Mycobacterium tuberculosis)
4 Basic Characteristics of Immune Responses
- Most invertebrates can clear an infection, but soon are susceptible again
- Not all immune responses are successful- chronic disease or death
- Immune responses can result in clearance of infecting pathogens
- For vertebrates successful immunity usually leads to IMMUNE MEMORY
What is immune memory?
Ability of the immune system to respond more rapidly and effectively to pathogens that have been encountered previously.
ex: Smallpox caused by the pox virus Variola major (~50% mortality)
Variolation
powdered scab is blown into the nasal passage.
1,000 years ago in China, dried & powdered smallpox scabs were used to immunize people.
History of smallpox variolation
- Started in China
- Smallpox variolation knowledge traveled in the Silk Road to the Ottoman empire (Turkey) & Africa)
- English diplomat’s wife (Lady Montagu 1715-1721) saw it in Constantinople (Turkey) & brought the idea to England.
- African slaves introduced it to Americans
He noted that English milkmaids get cow pox (mild) but not smallpox (deadly) in the late 1700’s- a new type of variolation
Edward Jenner
Difference in the variolation with smallpox vs. cow pox
Smallpox- scab powder put into cuts in the arm
- 1 to 2% mortality with smallpox variolation
Cow pox- no mortalities with cow pox variolation
3 Vaccine Types
- Attenuated- living (but weak) virus - e.g. cow pox
- Inactivated- killed whole pathogen
- Subunit- parts or components of pathogen
Immune “__________” in response to vaccine leads to immune memory that protects when the vaccinated encounter the infecting pathogen.
priming
Vaccination risks
- adverse effects following vaccination
- Anaphylaxis (allergic response)
- vaccine quality or handling errors
What is Anaphylaxis
a severe type of allergic reaction that involves two or more body systems (e.g., hives and difficulty breathing).
Reproduction ratio (without vaccination) : R0
the number of new infections caused by each infected person
R0 < 1
not an epidemic- infection will die out in the population
R0 > 1
(epidemic) infection will spread in a susceptible host population
Herd Immunity
- the proportion of a population that needs to be immune to prevent pathogen spread (achieve by infection or vaccination)
- Based on R0
- Proportion to vaccinate = 1- 1/R0 (ex: For SAR-Cov2 R0 is 3, so you’d need 66% vaccinated)
The more easily transmitted the pathogen, the _____(higher/lower) the population proportion that needs to be immunized to prevent spread
higher
How do we get infected?
Examples of viral entry routes
- conjunctiva
- respiratory tract
- alimentary tract
- urogenital tract
- anus
- arthropod
- capillary
- scratch, injury
- skin
Examples of diseases that enter can be transmitted through the eyes/mouth?
- measles
- Coronavirus
- Rhinovirus
- Influenza
- Herpes virus
This disease is linked to oral-fecal transmission
Poliovirus
Diseases linked to entrance to anus
STI: HIV, Herpes virus
Diseases that Arthropods carry (Goes through capillary)
- West Nile virus
- Yellow fever
Diseases that can be transmitted by scratch, injury to skin
Contact with blood/secretions
- Hepatitis B virus, rabies, Ebola
Type of barriers in resisting infection
- behavioral
- biological
- physical
- chemical
examples of physical & chemical barriers in resisting infections
- enzymes in mucus, tears and saliva
- mucus and intact mucous membranes
- cilia in respiratory tract trap foreign material
- acid in sweat & sebum (pH 4.5-6)
- acid in stomach (pH 2)
- antibacterial proteins and zinc in semen
- competition from commensal bacteria in gut and genital tract
TRUE or FALSE
Skin covers ~2 m2, while mucous membranes cover ~400 m2
TRUE
Mucus
- line the GI, respiratory and genitourinary tracts.
- thin, permeable barriers
- gas exchange, food absorption, reproduction
These cells secrete mucus which traps microbes
Goblet cells
Ciliary escalator
- ciliated epithelial cells in trachea and nasopharynx. Cilia push bacterial cells back up
- bacteria trapped by mucous and coughed out or swallowed and killed by stomach acid
Mechanical removal
process of physically flushing microbes from the body through coughing and sneezing
Normal (and helpful) microbial flora
- biological barrier to infection
- present on all body surfaces that are exposed to the environment
- eyes, mouth, nose and throat, large intestines, urogenital system, even skin.
- generally, areas of higher moisture contain higher populations of normal flora.
How does normal flora help to prevent infection?
Microbial antagonism: normal flora inhibits colonization by pathogenic microorganisms through: occupation of habitat and competition for resources
Chemical barriers
enzymes that can degrade microbial cell walls in saliva and Anti-microbial peptides or AMPs
AMPs can punch holes on microbe membranes
Anti-microbial peptides
part of an ancient defense system
Lymph
yellow fluid that surrounds all tissues.
‘Captured’ pathogens are taken to the closest ________ or to _____ where circulating lymphocytes transit to see if they recognize it.
lymph node or spleen
______ screens the blood while _______ screen the bodies tissues.
spleen, lymph nodes
Spleen
loaded with immune cells of various types
