CH 1: Intro to the Immune System Flashcards
What is immunology?
Study of the physiological mechanisms that humans and other animals use to defend their bodies from invasion by pathogens
- study of the immune system
How does our body defend itself against pathogens?
immune system
3 broad categories of defense
- Physical & chemical barriers
- Innate response (born w/ it)
- divided into immediate & induced - Adaptive response
Pathogen
Any organism w/ the potential to cause disease
- can habitually cause disease or be opportunistic
Opportunistic
- normally already in our body at normal levels…occurs when at high levels
- will not always have the opportunity to cause disease
- must have certain conditions met
What does it mean to be immune to infection?
Built up resistance to a disease/infection
How do we become immune?
- natural selection
- vaccines
Immunization (vaccination)
Procedure to prevent severe disease by prior exposure to the infectious agent in a form that cannot cause disease
- purposeful exposure
- adaptive response
Immunization: history
- 1st used against smallpox in 18th century
- Lady Mary Wortley Montagu
—-small amounts of smallpox virus - Edward Jenner = cowpox
—-similar to smallpox, but not deadly
—-father of immunology
variolation
Make a cut in non-infected persona & expose them
Different forms of vaccines
- mRNA
- dead pathogens
- can mutate virus, “killed off” vaccines
Commensal microorganism
Habitually lives on or in the human body; normally does not cause disease & can be beneficial
- can make vitamins, process digested food, and protect against disease
- 1000+ microorganisms live in healthy adult gut, adding 10 lbs body weight
Commensal microorganism pt 2
- the reason why we lose lbs when given antibiotics…
- microorganisms died, but will regrow
- in gut, skin, etc
- take up space INSTEAD of pathogens
Microbiota
Community of microbial species that inhabit a specific niche in the human body
- skin, mouth, gut, vagina
vaginal vs c-section
importance of early exposure to microorganisms
Colon
The colon is colonized by large numbers of commensal bacteria
- antibiotics kill many of these com. bacteria
- pathogenic bacteria gain a foothold & produce toxins that cause mucosal injury
- rbc & wbc leaks into gut between injured epithelial cells
Four types of pathogenic organisms
- Viruses: intracellular (need a host)
- Fungi: extracellular
- Bacteria: extracellular
- Parasites: extracellular
Defenses (extracellular)
scratching, diarrhea, vomitting
Barriers help keep what away?
pathogens
Relationships of pathogens and humans change over time
Most pathogenic organims evolved adaptations to allow them to invade the host, replicate in them and be transmitted
- “new” pathogens often cause high mortality (ebola)
- rapid death of host not good for pathogen
Human population in the evolution of pathogens
- evolve a degree of built-in genetic resistance
- acquire lifetime immunity to endemic diseases
endemic diseases
ubiquitous and people often exposed in childhood
- measles, chicken pox
Pathogens evolve to become..
Less pathogenic
- mortality bad for both humans & pathogens
Epithelium
Layers of cells that line the outer surface & inner cavities of the body
- strong barriers: skin, hair, & nails (provides chemical & physical barrier)
- more vulnerable: mucosal surfaces (mucosae)–secrete mucus, thick fluid that protects epithelial cells from damage and infection
All epithelia produce what?
Antimicrobial peptides
- kill pathogens by perturbing their membranes
Tears & saliva
Secrete lysozyme that degrades bacterial cell walls
- level of protection
- ex : dust in your eyes
Stomach & vagina
Very acidic
If barriers are breached…
Innate immune response
Innate immune response
Born with; initiated immediately upon infection
- non-specific, localized defense against wide range of pathogens
- 2-part response
Innate immune response: 2-part response
- Recognition that a pathogen is present - soluble proteins & cell-surface receptors bind to the pathogen & its products or to altered human cells
- Recruitment of effector mechanism - processes used to destroy & remove pathogens
Effector mechanisms
- Effector cells
- Complement
Effector cells
Engulf bacteria, kills virus-infected cells, or attack parasites (macrophages, NK cells)
Complement
Serum proteins that mark pathogens in order to attack them or alter effector cells
Innate immunity
Host defense mechanisms that act at start of infection
Pathogen-recognition mechanisms
- Bacterial cell surface induces cleavage & activation of complement
- One complement fragment covalently bonds to the bacterium, the other attracts an effector cell
- The complement receptor on the effector cell binds to the complement fragment on the bacterium
Effector mechanisms
The effector cell engulfs the bacterium, kills it, and breaks it down
Innate immunity (general process)
- Healthy skin is not inflamed
- Surface wound introduces bacteria, which activate resident effector cells to secrete cytokines
- Vasodilation & increased vascular permeability allow fluid, protein, and inflammatory cells to leave blood & enter tissue
- The infected tissue becomes inflamed, causing redness, heat, swelling, & pain
Edema
Swelling
Cytokines
Soluble proteins secreted by cells to change behavior of surrounding cells
- produced when cells detect infection; react w/ other cells to trigger innate immune response
- make blood vessels leaky to allow fluids & other things to exit blood vessel & enter the infection
Inflammatory cells
WBCs present in inflamed tissues; contribute to inflammation
If infections outrun innate immune responses
Adaptive immune response
Adaptive immune response
Response of antigen-specific B and T lymphocytes to antigen
- involves development of immunological memory
- adapts to the infecting protein
- highly specific (of the type of cell)
- evolved only invertebrates
Lymphocytes
B, T, and NK WBCs
- B & T are small
- WBCs are large, also involved in innate response
Antigen
Molecule or molecular fragment recognized by an antibody or B or T cells
- may also be proteins, toxins, etc
Recognition mechanisms: Innate vs Adaptive response
Innate:
- rapid response (hrs)
- fixed
- limited number of specificities
- constant during response
Adaptive:
- slow response (days to weeks)
- variable
- Numerous highly selective specificities
- improve during response
Innate and Adaptive responses have common what?
Common effector mechanisms for the destruction of pathogens
Specificity of adaptive immune response
Lymphocyte receptors encoded by genes that are cut, spliced and modified during lymphocyte development.
- clonal selection
- clonal expansion
Clonal selection
Stimulation of a small subset of pathogen-specific lymphocytes for proliferation
Clonal expansion
Proliferation and differentiation of selected lymphocytes
- large clones of antigen-specific lymphocytes generated to fight the infection
Adaptive immune response is faster/slower than innate immune response?
Slower!
Different receptors…
Different antigens
Memory cells
Lymphocytes selected during an adaptive immune response that persist after the infection
- allow for immunological memory
- subsequent infection by same pathogen elicits stronger and faster adaptive immune response
Acquired/protective immunity
Adaptive immunity provided by immunological memory
Primary immune response
First encounter with pathogen
Secondary immune response
All subsequent encounters with that pathogen
- anything after primary response, bc don’t know how many times exposed
In order for adaptive response to be activated what happens first?
NEED innate response first
Vaccinations induce what?
Immunological memory
- B & T cells memory
- adaptive responses contingent upon innate responses…so vaccines must induce BOTH
