Lecture 9: The Adaptive Immune System Flashcards
The Adaptive Immune System
Acquired
Very specific
Has a memory component
Consists of two components:
- Humoral (antibody mediated) immunity
- B cells are respon. for this - Cell mediated immunity
- T cells (*specifically cytotoxic ones) are respon. for this
• Acquired (meaning)
NOT born with - instead, develops over course of your life b/c of pathogens your encountering on daily basis
- Begins as soon as a pathogen is encountered for the very first time
- Adaptive response will not occur until a pathogen is encountered
• Very specific (meaning)
• Very targeted to a specific feature of a given bacterium, virus, toxin
- going after something about E.coli, something about HIV or SARS-COV-2 (not random or non-specific)
- • Immunity to one pathogen will not confer immunity to another
- NOT cross-reactive responses
• Has a memory component (meaning)
• Produces a more effective response when a pathogen is encountered for the second time-faster and stronger
- if you’ve seen something and mounted a response against it today it, its something you will have memory and protection against net time you encounter material
- ~long-term protection b/c it remembers any adaptive interaction that took place before
- 2nd response is much quicker & will produce higher levels of immune activation, immune response & stronger response overall
Antibodies:
Something YOU make to protect you
• Proteins produced by the immune system that bind and inactivate foreign antigen
Immunogens:
Any foreign material that has the ability to active the adaptive immune system
- NOT YOU
- get the attention of adaptive immunity
• Normally protein, polysaccharide, lipid material *=ALL ORGANIC
Epitopes:
• The actual portion of the ANTIGEN that binds to the antibody
- each spike protein will be referred to as an antigen & antibodies binding to this are doing so with specific regions referred to as epitope
• A single antigen will have more than one epitope
- each antibody will have their own specific epitope that they bind to, in order to induce protection & nutrilization
• Increases the ability of an antigen to activation the immune system –> immunogenicity
- some antigens so a much better job of activating the immune system then others
– some antigens will be less immunogenic & won’t have same opp. to activate immune system & that means some antigens are better for vaccination then others b/c they’ll be stronger in terms of how they turn on the immune system
• Each epitope requires a distinct antibody
Hapten:
• LOW MOLECULAR WEIGHT compound that is too small on its own to activate adaptive immunity
- not big enough to get the attention of the immune system
• NOT IMMUNOGENIC
- Can bind to other molecules such as protein in blood and tissues
- Becomes strongly immunogenic
- An allergy forms
- Ex) penicillin
Describe penicillin
antibiotic used to treat infection
- penicillin is a HAPTEN that specifically will bind to PROTEINS that are be present in blood & tissues for ex
- & whole thing gets attention of immune system
- & is said to be STRONGLY IMMUNOGENIC (allows opp. for immune system to react against penicillin which you don’t want)
- whole point of penicillin was to help you treat an infection (not to kill off drug & remove from insides of body)
Antibodies (Ab) are…
glycosylated protein molecules
- b/c are AA sequences that have sugar groups that are added to various locations
Antibodies (Ab) are AKA
Also called IMMUNOGLOBULINS (Ig)
Describe the structure of antibodies
Consist of 4 subunits
• TWO identical HEAVY chains- have many aa’sn
• TWO identical LIGHT chains- have less aa’s
- CHAINS are assembled creating THREE distinct regions
- 2 identical variable regions (Fab regions)
- 1 constant region (Fc region)
Explain the 2 identical variable regions (Fab regions)
formed from heavy & light chain that come together
• Provide the specificity of the antibody
- allow foreign material to initiate a response
- get bound to that foreign material specifically at that site & if you want to bind a diff kind of foreign matter, you will then need a brand new antibody in order to do it
- has to be more than 1 antibody when you have foreign material that has diff components or antigens b/c each antibody is so specific
think: same way police has to interact with bad guys (Fab region)
Explain the 1 constant region (Fc region)
b/c not an infinite # of possibilities but instead are only 5
- type of Fc region will determine which of the 5 we have
• Allows for INTERACTION (talk) with immune cells
- Fc region allows antibody to be able to send messages & to be able to communicate with other elements of the immune system
• Based on differences in the Fc region there are FIVE different types of antibody
think: in Fc region, police has opp. to interact with other members of the force, to communicate diff types of info they found
Classes of Antibody
- Immunoglobulin M (IgM)
- Immunoglobulin G (IgG)
- Immunoglobulin A (IgA)
- Immunoglobulin D (IgD)
- Immunoglobulin E (IgE)
Immunoglobulin M (IgM):
Pentameric
• Five different antibody units form IgM; each antibody can bind 2 identical antigens
• Always the first antibody to be produced in
response to an antigen; 1 st antibody that reacts to an infection which later on you can switch and produce different antibodies
• Primary antibody response
- Found on the surface of B lymphocytes
- Remains in the blood; b/c so large even with increased pore size during inflammation
- Unable to enter the tissues
- Low affinity for antigen; doesn’t bind with strong affinity
- Very good at agglutination; can bind 10 identical antigens
. Immunoglobulin G (IgG):
- Monomer; only binds 2 identical antigens
- Most predominate antibody in the blood
- Also present in the tissues; foot and muscle
If you go to doctor b/c you think you contracted the HIV, they’ll ask you q’s about when you think that might’ve happen but also ask you to come back & get retested. What is the reason?
reason; you always start by producing IgM against foreign material once its produced you switch to diff type of antibody after initial infection
for HIV you begin by Igm then switch to IgG test used looks for IgG, if you have just been infected you are not producing antibody or IgM
IgG is produced after infection has taken place so ppl get tested 3 and 6 months after bc you will be producing IgG
Immunoglobulin A (IgA):
Dimeric; bind 4 antigens • Secreted at mucosal sites • Saliva, tears, mucous • Important defense against respiratory, reproductive, digestive tract infections
Immunoglobulin D (IgD):
Monomer
• Located on the surface of B cells
• Important in activation of B cells to begin
producing antibody against a specific antigen
Immunoglobulin E (IgE):
Immunoglobulin E (IgE):
• Monomer
• Binds to receptors located on the surface of
mast cells and basophils
• Binding of IgE-antigen complex triggers
degranulation and histamine release
• Allergy
Describe how Ige causes release of histamine
Antibody attaches with the FCIge receptor on the basophils and mast cells
allergen in bound to the fab region of antibody
outcome- degranulate in response to allergen bound to Ige bound to FC Ige receptor and histamine gets released causing allergic symptoms
List then 5 major antibody functions
- Neutralization:
- Opsonization:
- Agglutination:
- Antibody mediated cytotoxicity:
- Complement activation
. Neutralization:
Antibodies bind to antigen blocking attachment
sites
• Prevents bacteria, virus and toxin entry into
tissues and host cells