Seminars 1/2 (Ben) - Intro + Ag/Ab Tests Flashcards
What are the 4 main features of adaptive immunity?
- Specificity
- Sensitivity - small amt antigen can trigger
- Memory
- Selectivity - cell clone with appropriate receptor for antigen will proliferate more
What are the prefixes for 3 types of antigens according to their origin?
- Auto - self antigen
- Allo - non-self but same species
- Xeno - non-self, different species
What is the basic difference between the epitopes bound by TCRs and BCRs?
- BCR - binds conformational epitopes on unprocessed, whole antigen molecules
- TCR - binds linear epitopes presented on MHC after APC processing
What happens if bone marrow has a functional defect?
(this was presented as an MCQ on the seminar PPT… maybe test material)
- amt of circulating blood cells is reduced (pancytopenia) and severe, recurrent infections occur
What happens if a baby loses their thymus during a surgical procedure?
(another PPT MCQ)
- Peripheral T cell function may be affected, leading to early immune senescence
What is immunophenotyping?
- 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
What CD molecule is common to all T cells?
How does its cellular location change over the course of T cell maturation?
CD3
- transitions from intracellular icCD3 to normal CD3 on the cell membrane between “early thymocyte” and “common thymocyte” stages
What CD molecule is common to all NK cells?
(both NKT and regular NK)
CD56
(NKT is CD3+, NK is CD3-)
What CD molecule is present on all B cells?
CD19
What is a consequence of lymph node removal?
(another PPT MCQ)
- lymphedema can develop as a result of disturbed lymph drainage
What are the different parts of a lymph node and the types of cells in each?
- Paracortex - T + dendritic cells
- Cortex - B cells + macrophages
- Germinative Center - dividing B cells, plasma cells + macrophages
- Follicle - B cells
- Medulla - plasma cells + macrophages
Through what special kind of blood vessel do lymphocytes enter secondary lymph organs?
High Endothelial Vessels
- in all secondary lymph organs except spleen
- cuboidal endothelial cells with receptors for leukocyte interaction
What is a sentinel lymph node?
- the first lymph node in a lymph node bed to receive drainage from a tumor
- “staging” of cancers is based on sentinel node biopsy
What is the consequence of a splenectomy?
(another PPT MCQ)
- susceptibility to infections with encapsulated bacteria and immune memory reduction
What are the two types of mucosa-associated lymph tissue (MALT) and examples/locations of each?
- GALT (GI-associated) - tonsils, appendix, Peyer’s patches
- BALT (broncheoalveolar) - in lung parenchyme + bronchi
What is the consequence of a tonsillectomy?
(PPT MCQ)
- there is no direct immunological consequence
What is the total count of WBCs per liter of blood?
Men: 3.7 - 9.5 x 109 / L
Women: 3.9 - 11.1 x 109 / L
What are the lymphocyte counts in blood per liter?
Overall and for specific types.
- 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
What are the granulocyte counts in blood per liter?
Overall and for each type.
- 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
What is the monocyte count in blood per liter?
Monocytes: 0.2 - 0.9 x 109
What kind of bonds form between antigens and antibodies?
- many non-covalent bonds = strong connection
- H bonds, ionic bonds, VdW interactions + hydrophobic interactions
- is irreversible
What are polyclonal vs. monoclonal antibodies?
- 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
What is affinity in terms of antibodies?
How is it quantified?
- 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]
What is avidity in terms of Ag-Ab interactions?
- 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
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
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
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
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)
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)
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)
What factors affect precipitation?
(3)
- Valence - # of “arms” by which Ab can bind Ag (IgM pentamer vs. IgA dimer)
- Temperature - lower temp. encourages precip.
- Chemical Factors - solubility-decreasing substances such as PEG
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
Describe simple radial immunodiffusion.
AKA Mancini method
- Patient sample loaded into wells of gel containing Ab specific to Ag in question
- Ag diffuses into gel + forms ring of precipitate where [Ag] = [Ab]
- Diameter is proportional to log [Ag]
Describe double radial immunodiffusion.
AKA Ouchterlony method
- Ag and Ab placed in seperate wells in gel + diffuse toward each other
- Precipitate line forms where [Ag] = [Ab]
- If [Ag] in sample is higher, Ag will move further toward Ab well + thus dilute to match [Ab] (and vice versa)
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.
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)
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)
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
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.
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
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)
How can hemmaglutination occur without antibodies?
Viral proteins (eg mumps, flu) can induce agglutination
