QUESTIONS

1. What is the difference between �Homocytotropic� & �Heterocytotropic� antibodies?
    
2. When an antibody binds to a mast cell, is it bound their permanently?
    
3. Allergens tend to be proteins between 10,000 and 70,000 Daltons.  What is the significance of this size range?
    
4. What is the usual age group of dogs affected by SLE?
    
5. What is the most common clinical feature of SLE?  What is the next most common clinical feature of SLE?
    
6. True or False:  There is such a well described  immune-mediated ruptured cruciate ligament in the dog.
    
7. What feline virus is most strongly associated with the Reiter�s form of feline chronic progressive polyarthritis?
    
8. How might you diagnose the Reiter�s form of feline chronic progressive polyarthritis?
    
9. How does the direct Coombs test work?
    
10. How does the indirect Coombs test work?
     
11. How does the PF-3 test work?
     
12. How do you do an LE cell prep?
     
13. What is a Tart cell?
     
14. What is the usual antibody class produced by multiple myeloma in the dog?  In the cat?
     
15. What is a Bence-Jones protein made of?
     

ANSWERS

1. The IgE class of antibodies are homocytotropic.  This means that they can sensitize the mast cells of  only one species.  IgM, IgG, & IgA are heterocytotropic and can sensitize the mast cells of other species.  (Recall that the Fc portions of antibodies bind to mast cells.  When the mast cell is covered with IgE it is said to be �sensitized.�)
    
2. Hell no.  Antibodies eventually unbind  from the mast cell.  Non-IgE antibodies only bind for 12-24 hours.  IgE binds for 3-6 weeks.
    
3. Proteins smaller than 10,000 Daltons cannot attach between two adjacent membrane bound antibodies.  Proteins larger than 70,000 Daltons tend not to be absorbed across mucous membranes.
    
4. Dogs afflicted with SLE are usually 2-4 years of age.
    
5. The most common feature of SLE is a cyclical, non-antibiotic responsive fever.  The second most common feature of SLE is polyarthritis in the dog and glomerular disease in the cat.
    
6. There sure is.  It tends to occur in larger breeds. 
    
7. The feline syncytium forming virus has been found in 100% of cases with the Reiter�s form of feline chronic progressive polyarthritis.  It should be noted that 60% of cases were FeLV+.
    
8. Features of feline chronic progressive polyarthritis include:
   
   - osteoporosis around the joints seen on x-rays
   - after several weeks obvious periarticular osteophytes are seen
   - large numbers of PMNs are found in the synovial fluid.
   - joints are very painful, lymph nodes enlarge and there is usually
     a fever.
    
9. Here�s how the direct Coomb�s test works:
   
   - take some patient red cells, wash them, and resuspend them in
     saline (get rid of the serum)
   - add anti-dog (or anti-cat) IgG in different dilutions so the red
      cells will coat if they have dog (or cat) IgG on their surfaces
   - If agglutination is found, the cells were coated with patient IgG
     and the test is positive.  If agglutination is not found, the cells
     were just plain cells without any antibody coating and the test is
      negative.
    
10. The indirect Coombs test is a little different.  It tests patient serum for antibodies instead of testing patient cells for antibody coating.  Here, patient serum is incubated with normal cells.  The cells are washed and then the above procedure is done.
     
11. Here�s how the PF-3 test works:
    
    - incubate washed platelets from a normal dog with patient serum.
       (And with normal serum as a control)
    - Add clotting factors to clot the platelets
    - a fast clot indicates that platelet factor 3 was released from the
       platelets especially quickly.  One infers that antibodies must
       have damaged the platelets and such a test would be positive                  
       for anti-platelet antibodies.  I have in my notes that in 70% of
       true immune-mediated thrombocytopenias this test is falsely
       negative. :(
     
12. Here�s how the LE prep works:
    
    - strain a sample of clotted blood from the patient.  This releases
      free nuclei.
    - incubate the sample, centrifuge & smear the buffy coat
    - Look for PMNs or monocytes that have phagocytized a free
      nucleus. But remember that the nucleus must be homogeneously
      staining.  This homogeneity of staining indicates the presence of
      antinuclear antibody.
     
13. A tart cell ins a PMN or a monocyte that has phagocytized a nucleus that is not homogeneously staining.  This is not an LE cell and does not indicate SLE.
     
14. In the dog the most common antibody class of multiple myeloma is IgA.  In the cat it is IgG.
     
15. Bence-Jones proteins are made of Ig light chains.  They form from the catabolism of large amounts of antibody as in the case of multiple myeloma.  (Sometimes monoclonal antibodies are called �M proteins� so  you could say that Bence-Jones proteins come from the catabolism of large amounts of M protein.