Seminars 1/2 (Ben) - Intro + Ag/Ab Tests Flashcards
1
Q
What are the 4 main features of adaptive immunity?
A
- Specificity
- Sensitivity - small amt antigen can trigger
- Memory
- Selectivity - cell clone with appropriate receptor for antigen will proliferate more
2
Q
What are the prefixes for 3 types of antigens according to their origin?
A
- Auto - self antigen
- Allo - non-self but same species
- Xeno - non-self, different species
3
Q
What is the basic difference between the epitopes bound by TCRs and BCRs?
A
- BCR - binds conformational epitopes on unprocessed, whole antigen molecules
- TCR - binds linear epitopes presented on MHC after APC processing
4
Q
What happens if bone marrow has a functional defect?
(this was presented as an MCQ on the seminar PPT… maybe test material)
A
- amt of circulating blood cells is reduced (pancytopenia) and severe, recurrent infections occur
5
Q
What happens if a baby loses their thymus during a surgical procedure?
(another PPT MCQ)
A
- Peripheral T cell function may be affected, leading to early immune senescence
6
Q
What is immunophenotyping?
A
- specific labeling of surface/intracellular markers to identify a cell population
- done with Ag-AB reactions
- can help identify leukocyte subpopulations, as well as their functional/developmental states
- mostly looks for CD (Cluster of Differentiation) molecules
7
Q
What CD molecule is common to all T cells?
How does its cellular location change over the course of T cell maturation?
A
CD3
- transitions from intracellular icCD3 to normal CD3 on the cell membrane between “early thymocyte” and “common thymocyte” stages
8
Q
What CD molecule is common to all NK cells?
(both NKT and regular NK)
A
CD56
(NKT is CD3+, NK is CD3-)
9
Q
What CD molecule is present on all B cells?
A
CD19
10
Q
What is a consequence of lymph node removal?
(another PPT MCQ)
A
- lymphedema can develop as a result of disturbed lymph drainage
11
Q
What are the different parts of a lymph node and the types of cells in each?
A
- Paracortex - T + dendritic cells
- Cortex - B cells + macrophages
- Germinative Center - dividing B cells, plasma cells + macrophages
- Follicle - B cells
- Medulla - plasma cells + macrophages
12
Q
Through what special kind of blood vessel do lymphocytes enter secondary lymph organs?
A
High Endothelial Vessels
- in all secondary lymph organs except spleen
- cuboidal endothelial cells with receptors for leukocyte interaction
13
Q
What is a sentinel lymph node?
A
- the first lymph node in a lymph node bed to receive drainage from a tumor
- “staging” of cancers is based on sentinel node biopsy
14
Q
What is the consequence of a splenectomy?
(another PPT MCQ)
A
- susceptibility to infections with encapsulated bacteria and immune memory reduction
15
Q
What are the two types of mucosa-associated lymph tissue (MALT) and examples/locations of each?
A
- GALT (GI-associated) - tonsils, appendix, Peyer’s patches
- BALT (broncheoalveolar) - in lung parenchyme + bronchi
16
Q
What is the consequence of a tonsillectomy?
(PPT MCQ)
A
- there is no direct immunological consequence
17
Q
What is the total count of WBCs per liter of blood?
A
Men: 3.7 - 9.5 x 109 / L
Women: 3.9 - 11.1 x 109 / L
18
Q
What are the lymphocyte counts in blood per liter?
Overall and for specific types.
A
- Total: 1.1 - 3.5 x 109
- T: 0.7 - 2.7 x 109
- B: 0.06 - 0.66 x 109
- NK: 0.2 - 0.4 x 109
19
Q
What are the granulocyte counts in blood per liter?
Overall and for each type.
A
- Total: 1.8 - 8.9 x 109
- Neutr: 1.5 - 7.4 x 109
- Eos: 0.02 - 0.67 x 109
- Baso: 0 - 0.13 x 109
20
Q
What is the monocyte count in blood per liter?
A
Monocytes: 0.2 - 0.9 x 109
21
Q
What kind of bonds form between antigens and antibodies?
A
- many non-covalent bonds = strong connection
- H bonds, ionic bonds, VdW interactions + hydrophobic interactions
- is irreversible
22
Q
What are polyclonal vs. monoclonal antibodies?
A
- Polyclonal - different antibody products of different B-cell clones recognizing different epitopes on the same antigen, normally produced in physiological immune response
- Monoclonal - antibodies specific to a single epitope, from a single B cell clone, sometimes produced in disease
23
Q
What is affinity in terms of antibodies?
How is it quantified?
A
- how strongly an antibody fits to its antigen
- expressed in terms of the equilibrium constant of the Ag-Ab complex
- Keq = [Ag-Ab] / [Ag] x [Ab]
24
Q
What is avidity in terms of Ag-Ab interactions?
A
- combined strength of all bond interactions btwn an Ab and its Ag
- ex: pentameric IgM with binding several epitopes on the same antigen has higher avidity than monomeric IgG with just one or two epitopes bound
25
What is _serum electrophoresis_ and what is it for?
* separation of serum proteins via an electrical current, based on their electrical charge
* used primarily to diagnose _myelomas_ or _gammopathies_
26
How does a normal _serum electrophoresis densitogram_ look?
How does it change in myeloma and polyclonal gammopathy?
* _Normal_: largest spike is albumin, gamma globulins are a low hump
* _Polyclonal_: a taller, but still broad, y-globulin hump
* _Myeloma_: an **M-spike** in the gamma region
27
What happens to a _serum electrophoresis densitogram_ in case of **chronic liver failure** and **chronic inflammation**?
* _liver failure_: a *relative* decrease in albumin and alpha/beta globulins, increase in gamma-glob.
* _inflammation_: a *relative* albumin decrease, with an acute phase protein + Ig increase showing in the alpha, beta + gamma bands
28
What are some disease cause by _immune complex overproduction_ ?
* _Via endogenous ABs_: ABO/RH incompatibility, hemolytic anemia + SLE
* _Via exogenous ABs_: "serum sickness" caused by a reaction to exogenous antibody administration (e.g. allergic reaction to an antivenom)
29
What is the difference between _turbidometry_ and _nephelometry_?
Both measure levels of proteins in liquid samples (serum, CSF, etc.)
* **Turbidometry** - measures light intensity which makes it *directly* thru a sample (lower sensitivity)
* **Nephelometry** - measures light intensity which is *scattered* by a sample (higher sensitivity)
30
What is **precipitation** in terms of immunological reactions?
What is required for normal precipitation to occur?
(in terms of Ag/Ab concentrations)
* soluble antigens forming soluble Ag-Ab complexes can be made insoluble/visible in the lab via *physical* (decreased temp.) or *chemical* (polyethylene glycol) methods
* requires similar Ag/Ab concentrations (**equivalence**)
31
What factors affect precipitation?
| (3)
1. **Valence** - # of "arms" by which Ab can bind Ag (IgM pentamer vs. IgA dimer)
2. **Temperature** - lower temp. encourages precip.
3. **Chemical Factors** - solubility-decreasing substances such as PEG
32
What is the "Reynaud phenomenon"?
* bluish-black tips of digits due to precipitation of circulating immune complexes at lower temps
* common in immune diseases with incr. circulating complexes
33
Describe _simple radial immunodiffusion_.
AKA **Mancini method**
1. Patient sample loaded into wells of gel containing Ab specific to Ag in question
2. Ag diffuses into gel + forms ring of precipitate where [Ag] = [Ab]
3. Diameter is proportional to log [Ag]
34
Describe **double radial immunodiffusion**.
AKA **Ouchterlony** method
1. Ag and Ab placed in seperate wells in gel + diffuse toward each other
2. Precipitate line forms where [Ag] = [Ab]
3. If [Ag] in sample is higher, Ag will move further toward Ab well + thus dilute to match [Ab] (and vice versa)
35
Describe **immunoelectrophoresis**.
* Patient + control serums are applied to separate round wells in gel on opposite sides of a long, narrow well
* Serum proteins are electrophoretically separated
* A complete _polivalent Ab set_ from diff organism (eg horse) is applied to long well
* Sample serum proteins diffuse towards Abs + form multiple arcing precipitate bands in gel
* Can compare size, density + positioning of control bands to sample bands to look for increased concentrations, etc.
36
Describe **immunofixation** + its purpose.
To detect a *specific antibody isotype* (antibodies in sample are the antigens for the experimentally applied antibodies):
* Same sample (urine, serum, etc.) is run thru electrophoresis in 6 lanes
* "Monospecific" antibodies for each type of Ab heavy + light chain (mu, alpha, gamma, kappa, lambda) are each applied to a lane
* Precipitates form where the sample's elevated ABs react with the applied ABs (ex: if IgG-lambda is elevated, precipitate forms in the gamma + lambda lanes)
37
What is an **antibody titer**?
* a test for the maximal dilution of an Ab solution that will still give a positive agglutination result when combined with a fixed amt of antigen
* the result is expressed as the inverse of the dilution (in pic below result = **160**)
38
What is _direct_ vs. _indirect_ agglutination?
* _Direct_ - binding of primary antibodies with antigens of cells results in agglutination
* _Indirect_ - secondary antibodies bind to Fc region of primary ABs against cellular antigens + induce agglutination
39
What is _passive agglutination_?
What are 2 examples of lab tests using this method?
* Latex beads without surface antigens are coated with a known antigen or antibody + mixed with serum to check for presence of Ab/Ag
* Tests for _r__heumatoid factor_ (serum IgM autoantibodies against self IgG) and _CRP_ use passive agg.
40
What are the structures of the ABO antigens?
* **O antigen** - has terminal galact-/fucose sugars
* **A antigen** - an _N-acetyl-galactosamine_ on O Ag
* **B antigen** - a _galactose_ on O Ag
41
Describe the _microcolumn_ _test_.
What is it for?
Tests the amount of ABO antibodies in patient serum with known cells/antigens or vice versa
* Add sample + knowns to microcolumn containing *anti-IgG, anti-IgM* and *anti-C3d* (help indirect agglutination)
* *Sepharose* beads at bottom of well will catch agglutinated complexes upon centrifugation (+ result) or non-agglutinated cells will flow to bottom (- result)
42
How can hemmaglutination occur without antibodies?
Viral proteins (eg mumps, flu) can induce agglutination
