immunologic tests

Question 1

What is the difference between a direct and an indirect test?

Answer 1

in a direct test you are able to visually see what is bound to the Fab portion of the antibody;
in an indirect test you are not able to see what is bound to the Fab portion of the antibody so you must attach something to the Fc to visualize the results

Question 2

In the three types of hemeagglutination tests, what are you looking for and what would a positive result look like?

Answer 2

1) Ig to RBC, agglutination
2) virus able to bind RBC, agglutination
3) Ig to virus that is able to bind RBC, no agglutination

Question 3

What type of agglutination test would use to look for antibodies to a (small!) soluble antigen?

Answer 3

a passive agglutination test

Question 4

What substances are present in a HAT plate?

Answer 4

hypoxanthine, aminopterin, thymidine

Question 5

In a HAT selection, why do unhybridized B cells and myeloma cells die?

Answer 5

the B cells are not immortal so they die naturally after 1-2 weeks
the aminopterin inhibitis purine synthesis through DHFR and mylelomas do not have the HGPRT enzyme and/or thymidine kinase for the alternate pathway

Question 6

In a direct ELISA, what is attached to the plate and what are you looking for?

Answer 6

antibody to the chosen antigen, antigen (virus) particles in the patient’s serum

Question 7

In an indirect ELISA what is attached to the plate and what does a positive test look like?

Answer 7

antigen, color or light production from the enzyme linked secondary antibody

Question 8

What’s happening in a positive competitive ELISA?

Answer 8

most antigen from the patient sample bind the antigen specific antibody added in solution and are washed away leaving nothing/very little bound to the antigen at the bottom of the plate (so no or much less color or light reaction)

Question 9

If you find IgM in a patient sample taken at the onset of symptoms, what would that tell you about the illness in a neonate vs. an adult?

Answer 9

neonate= in utero infection/TORCH agent
adult= a primary or current infection, not specific to any infectious agent

Question 10

What would the absence of IgG to an infectious agent in acute and follow up samples indicate?

Answer 10

1) no current or past infection
2) patient is immunocompromised
3) you took the follow up sample too early and they have not yet switched from IgM production to IgG

Question 11

What serodiagnostic test is used to test for Rubella, CMV, and syphilis?

Answer 11

immune status evaluation (IgM, G, A, E)