exam 1 Flashcards
Describe Eosinophils
Bilobed nucleus, granulocyte, phagocytic
High affinity for IgE, low affinity for IgG
Key role in fighting parasitic infections
small role in allergic rxns
Important in the pathogenesis of asthma and other chronic inflammatory diseases
Describe Basophils
Granulocyte
Cross linking with Fce receptors with IgE and its antigen -> degranulation
Minor role in Allergic reactions
granules contain histamine and vasodilators
Mast cells
Found in CT tissues and skin, granulocyte
High affinity surface for IgE
*play a major role in allergic responses
Cross linking with Fce leads to degranulation
Granules contain histamine and vasodilators
Layering
2 types: innate and adaptive
Redundancy
A single pathogen can be fought by the immune system multiple ways (e.g. different phagocytes, different Abs)
The 2 immune responses
First: recognition that a pathogen is present (cell-surface receptors, serum proteins)
Second: recruitment of effector mechanisms to kill and eliminate the pathogen (e.g. Abs and complement)
Innate immunity
Prevents establishment of a pathogen in most cases
non-specific (mucus, skin), always present at basal levels (always on)
elements you are born with, physical/anatomical barriers (skin, blinking)
-Macrophage, neutrophil, enzymes, NK cell, fever, inflammation, complement, cytokines
Adaptive immunity
Acquired and specific to an antigen
-slower to develop activated B&T cells increase in number (clonal expansion)
-Provides memory
2 types: Humoral (Ab think missiles) and Cell mediated ( think hand-to hand combat T cells)
Cell mediated immunity
adaptive, protects against INTRAcellular pathogens (virus)
T cells: CD8+ CD4+ Th1 CTLs
direct killing by T cells
Humoral immunity
adaptive, involves production of Abs Protects against EXTRAcellular pathogens (bacterial) B cells T cells: CD4+ Th2 Complement
Cellular components of Adaptive immunity
Naïve cells (yet to encounter their antigen/unprimed) before activation
Effector cells: carry out immune function
Memory cells: circulate and await next encounter with the antigen( can quickly become effector cells
Granulocytes: Basophils, eosinophils, mast cells
Antigen presenting cells (APCs)
adaptive immunity
Dendritic cells (#1), macrophages, B cells
All have MHC 1 and MHC 2
-Engulf pathogens, break them down into smaller pieces and present them to T cells
Non-cellular components of the adaptive immunity
Antibodies- produced by activated B cells
Cytokines- produced by activated immune cells (T cells, macrophages, NK cells)
Complement - proteins circulating in the blood stream
Papain
3 pieces 2 Fab (fraction antigen binding) 1 Fc (fraction crystallizable) Hinge present before Ab is treated with papain ( flexible region only present in CH3 domains IgG, IgA, IgD)
Fab
2 of them only when treated with Papain
-This portion can bind antigen
Contains VL, CL and VH, CH1
Fc
Only made when treated with Papain
1 piece includes most of the hinge region(below), CH2, CH3 (&CH4 if it’s present)
-opsonization occurs when the Fab portion binds antigen while the Fc portion is bound by Fc receptors on immune cell that phagocytose the antigen. (need Fab to opsonize)
-Delivers the Ab to specific anatomical sights
F(ab’)2
Only 1 piece made when treated with pepsin (think pepsi 1)
- single piece made up of both Fab regions and the hinge (Fc is not generated)
Hinge region
found between CH1 and CH2
-allows the Fab arms to open and close to accommodate binding 2 epitopes
Only present in Abs with CH3 domains (IgA, IgG, IgD)
J chain
Only present with polymeric IgA, IgM
- only 1 J chain per molecule
- J chain is required for polymerization and interacts with Poly-ig or pIg receptor to transport (transcytosis) of antibodies from basal side to the lumen
CH4
4 ME
CH4 domains are only on IgM and IgE
-No hinge region
Describe Neutrophils
1 phagocyte - releases defensins to punch holes in the membrane
Makes cytokines: IL-1,IL-6,IL-8,TNF-alpha
Most predominant Granulocyte, Polymorphonuclear cells
lives less than/equal to 2 days
50 billion at any given time
Hypervariable regions
Hypervariable region = complementarity-determining regions (CDR1,CDR2, CDR3) There are 12 CDRs per molecule: 3 from each L-chain and 3 from each H-chain (IgG has 12 CDRs, IgM has 60 CDRs, dimeric IgA has 12 CDRs)
8-11 stretch of AA that are extremely varied.
These AA make contact and form bonds with the epitope, and they are the exact region that determines antigen specificity
Framework regions
The remaining 80 AA of the V region between the CDRs show less variability.
There are 4 FRs in each V region (FR1, FR2, FR3, FR4)
Isotypes of Abs
Determines the Class (IgG, IgA, IgM, IgE, IgD)
e.g of an isotype IgG1k, IgM(lambda)
what determines Ab function and what are the 4 functions
CH region determines function and anatomical location Functions: Opsonize Neutralize Complement activation ADCC
IgM
Monomeric BCR, made exclusively as a PENTAmer, has CH4 domain Most predominant isotype made in response to T-independent antigens (need 2nd signal to class switch) -most efficient isotype for activating the classical complement pathway -Gengival cervicular fluid is a major source of Igm in saliva ONLY isotype made by a FETUS and infants until 4-6 months
IgG
Four subclasses in humans (in this order IgG1, IgG3, IgG2, IgG4) hinge region is the structural characteristic to distinguish subclasses
-Most predominant in serum( but not most abundant)
-Half live is the largest 23 days
Only isotype to cross placenta and is present in titers for 6 months
IgG1, IgG3, IgG2 activate the classical complement pathway
-Can bind Fc receptors to increase opsonization (IgG1 is the best opsonin)
-Can participate in ADCC (antibody-dependent cell-mediated cytotoxicity) when bound by Fc receptors on NK cell
***Production of IgG begins when an infant is 4-6 months old
IgA
2 subclasses (IgA1, IgA2) IgA1 is most predominant in serum (5:1 ratio)
ratio is 1:1 in mucosal secretions
-most abundant of all Abs in quantity made, 2nd in serum after IgG
Most predominant found in secretions (tears, saliva, mucus, breast milk)
IgA is in both serum (s) and Secretions (S)
IgA1
Most monomeric IgA is found in serum (s)
-is generally directed against protein epitopes
IgA2
Polymeric IgA, dimeric, found in secretions (SIgA), 24 CDRs
Is generally directed against polysaccharide epitopes
SIgA is secreted by salivary glands into the oral cavity
-helps protect from proteolytic cleavage
