Quiz 1 - Immune System, Immunoglobulin & Complements Flashcards
Antigen vs Immunogen
Antigen - combines with specific byproduct but does not necessarily trigger the initial immune response
Immunogen - triggers the immune response and combines with the byproduct of the response
All immunogens are antigens, but not all antigens are immunogens
Innate vs adaptive - which forms memory?
Adaptive
Innate vs adaptive - which is nonspecific and which is specific?
Innate = non-specific
-no previous exposure required
Adaptive = specific
Adaptive immunity consists of these two types of immunity
Humoral immunity = antibodies
Cell-mediated immunity = B/T cells
Humoral vs cell-mediated immunity - which is triggered in a viral infection? Which is triggered in a bacterial infection?
Viral = humoral and cell-mediated
Bacterial = humoral
This develops when self-reacting cells persist and are not destroyed
Autoimmunity
Innate immunity - two types of barriers
Physical - ciliated cells, skin
Chemical - sweat, fatty acid (acidic & salty), saliva, tears (lysozymes)
Innate immunity - two types of barriers
Physical - ciliated cells, skin
Chemical - sweat, fatty acid (acidic & salty), saliva, tears (lysozymes)
What cells are granulocytes and what are agranulocytes
Granulocytes = neutrophils, eosinophils, basophils
Agranulocytes = lymphocytes, monocytes/macrophages
Majority of lymphocytes are what types of cells?
T cells
True/False - all T cells are CD4 or CD8
False
-immature T cells do not have these receptors
All T cells have this CD receptor
CD2
Where do T cells acquire their CD4 or CD8 receptors
Thymus
The most abundant WBC cell in circulation is the…
Neutrophil
-55-75% of total WBCs
The majority of T cells are this subset of T cells…
CD4 Th
-66% (2/3)
CD4 vs CD8 - which is T helper and which is cytotoxic T cell?
CD4 = T helper
CD8 = cytotoxic
Helper T cells are divided into… What cytokines do they release?
Th1 = IFN-gamma, TNF
Th2 = IL-4, IL-5, IL-6
What are the functions of IFN-gamma and TNF?
Activate macrophages
What are the functions of IL-4, IL-5, IL-6?
Activate B cells to become plasma cells
Whenever you get a cut or wound, these cells are the first phagocytes to encounter pathogens
Neutrophils
Neutrophils migrate through blood vessels to tissue in a process called…
Diapedesis
Immature vs mature neutrophils - what does each look like?
Immature = non-segmented bands
Mature = multi-lobed, segmented
Where are monocytes and macrophages found?
Monocytes = blood
Macrophages = tissue
What are macrophages called in these tissues: lungs, liver, kidney, brain, bone
Dust cells Kupffer cells Mesangial phagocytes Microglia Osteoclast
These two cells increase in an allergic response
Basophils
Eosinophils
Eosinophilia is indicative of what 2 things?
Allergies
Parasitic infection
Antigen-presenting cells (3)
Dendritic cells
Macrophages
B cells
What 2 types of cells do NK cells target?
Virus-infected cells
Tumor cells
Basophils and mast cells are both involved in… Where can each one be found?
Inflammatory response
Basophils are circulating, mast cells are in tissues
MHC is also known as
HLA = human leukocyte antigen
MHC I and II - what types of cells are they found on?
MHC I = all nucleated cells
-not on RBCs (not nucleated)
MHC II = antigen-presenting cells
What are haptens?
Antigens that are weak immunogens. Can be combined with a larger molecule to make it more immunogenic
- haptens + alum
- seen in conjugated vaccines
Antibodies - composed of how many light and heavy chains?
2 heavy
2 light
Which part of the antibody is susceptible to a proteolytic cleavage?
Hinge
-bigger the hinge, the more susceptible
When an antibody is treated with either papain or pepsin, how many fragments are produced?
Papain = 3 fragments
2 Fab and 1 Fc
Pepsin = 2 fragments 1 F(ab')2 and 1 Fc
Which part of the antibody attaches to complement to activate them?
Fc
What distinguishes different classes of antibodies?
Fc
Antibodies - light chains are one of two types…
kappa
lambda
never both together
How many classes of antibodies are there and what are they?
5
IgG IgM IgA IgE IgD
The most abundant Ig is… How many subclasses does it have?
IgG
4 subclasses
The largest Ig is
IgM
This Ig is present in body fluids… How many subclasses does it have?
IgA
2
What is IgE involved in?
Allergies
Parasitic infections
What is the composition of the Fc region?
Heavy chains only
IgA has two forms… where is each found?
Monomer in circulation
Dimer in mucous secretions
-has secretory piece, which resists proteolysis
IgD are found on…
Mature B cells
- gone in plasma cells
- regulates B cell activation
Normal CD4:CD8 ratio
2:1
After maturation, naive B and T cells go primarily to this secondary lymph organ
Spleen
-germinal centers
Can blood smears differentiate B and T cells? What do clinical labs usually use?
No
Flow cytometry
First antibody to be produced during any infection is… One week later, this antibody appears…
IgM
-declines faster
IgG
-lasts longer
During a secondary infection to the same pathogen, the response time is… Large quantities of this antibody is produced…
Shorter/faster
IgG
Active natural immunity example
Infections
Active artificial immunity example
Vaccinations
Passive natural immunity example
Igs crossing placenta
Igs secreted in breast milk
Passive artificial immunity example
Gammaglobulins and abs injections
What is adoptive immunity
Anti-cancer treatment
Inject NK cells
-adopt another person’s immunity
Stages of B cell maturation (4)
Undifferentiated stem cell
Pro-B cell
Pre-B cell
Mature, naive B cell
B cell genes rearrange during this stage of B cell maturation
Pro B cell
Which chromosomes are heavy chain, kappa light chain, and lambda light chain genes located?
Heavy = 14
Kappa light = 2
Lambda light = 22
The antigen-binding site is on this part of the antibody
Fab or variable region
Do plasma cells express IgM or IgD?
No
Heavy and light chains are connected by this type of bond
Disulfide bond
B cells undergo this process to make them highly specific for epitopes on antigens
Gene rearrangement
What are the 3 types of antigenic determinants (epitopes)
Isotype
Allotype
Idiotype
Isotype - have differences in… What is its significance?
Constant region of heavy chains (Fc)
Different classes of antibodies
-IgM, IgG, etc
Allotypes - have differences in… What is its significance?
Minor differences in constant region of heavy chains; variation of alleles
Gives rise to different subclasses
-IgG1 -> 4
Idiotype - have differences in… What is its significance?
Hypervariable region of Fab
-light + heavy chain
Single clone of B cells can produce unique abs
Only Ig that can cross the placenta is…
IgG -only IgG2 subclass cannot cross
This Ig activates the classical complement pathway
IgG
IgA form dimers and IgM form pentamers that bind together via this component
J chain
Which Ig is most susceptible to proteolysis? Why?
IgD - long hinge region
What cells do IgE antibodies bind to? Via which portion of the antibody?
Mast cells
Basophils
via Fc region
-Fab binds to antigens, causing degranulation
Least abundant Ig
IgE
True/false - T cells can recognize antigen directly
False
Antigen needs to be bound to MHC
Complement - part of innate or adaptive immunity?
Both:
Innate
-bridges to adaptive
Adaptive
-activated by antigen-antibody complex
Where are most complement proteins produced?
Liver
-adipose, epithelial can also produce
How complement protects against bacterial infection (2)
Aids in phagocytosis/antigen presentation
Causes lysis (MAC)
Complement pathways (3)
Classical
Alternate
Mannose-binding lectin (MBL)
Classical vs alternate pathways - which is antibody-dependent and which is antibody-independent?
Classical = antibody-dependent
- MUST be antibody-antigen complex
- cannot be triggered by antigen alone
- C1 - C9
Alternate = antibody-independent
-pathogen cell wall, polysaccharide, etc
MBL pathway - how is it activated?
Bacterial carbohydrates interact with complement
-in younger people
All 3 complement pathways converge on…
C3
Which complement proteins form the MAC?
C5 - C9
People who lack complement are susceptible to infections by this bacteria…
Neisseria meningitidis
Complement components can be inactivated by…
Heat
- 56C
- heat labile
Most abundant complement protein
C3
Most important complement pathway
Classical pathway
3 steps of the classical pathway and what complement proteins are involved in each step
Recognition - C1q, C1r, C1s
Activation - C2, C3, C4
Membrane attack complex (MAC) - C5 through C9
What activates the classical pathway?
Antigen-antibody complex
- 1 IgM or 2 IgG
- IgM is better = pentamer
How does the MAC work?
Forms a pore/channel in the cell, causing electrolytes to leak out and water to gush in, causing lysis
What activates the alternate pathway?
Cell walls
-involves Factor D, Factor B, properdin
Why is the alternate pathway beneficial?
When infection does not produce enough/no antibodies
-need complement to fight infection
What is the CH50 assay?
Total hemolytic complement
Screening test for function of classical pathway
- based on ability of patient’s complement to lyse a standardized amount of antibody-coated sheep RBC
- low CH50 = deficient
- value of 0 = total lack of complement
What does a CH50 value mean?
Dilution that lyses 50% of RBCs
What is the AH50 assay? How is it different from the CH50?
Screening test for alternate pathway function
-uses rabbit blood cells instead of sheep RBC
What does an abnormal CH50 and AH50 indicate? What does just an abnormal CH50 indicate?
Defect in C3, or C5 through C9
-later complement defective
Defect in C1, C2 or C4
-initial complement defective
CD4 cells bind to this MHC class… CD8 cells bind to this MHC class…
CD4 - MHC II
CD8 - MHC I
Factor D, Factor B, and properdin are involved in which pathway?
Alternate pathway
