Chapter 9: Immunnodiagnostics

Question 1

Meaning of allotype? (Examples)

Answer 1

an allelic difference in the same ab isotypes that differ between people (subtle difference amongst individuals in their immunoglobulins due to heterogeneity)

(a person receiving pooled gamma globulins might react to these allotypic differences in the constant regions which may result in a type III HSR)

Question 2

If an ab molecule is digested with papain, where does cleavage occur?

Answer 2

above the disulfide bonds that hold the heavy chains together

Question 3

General function of Papain and Pepsin.

Answer 3

proteolytic enzymes that aid in digestion

Question 4

If an ab molecule is digested with pepsin where does cleavage occur?

Answer 4

generates one large fragment called F(ab’)2 and digested Fc fragment (think Pepsi in martini glass)

Question 5

Describe this figure

Answer 5

1. Start of infection the patient is in a state of ag excess
2. As patient begins to make an adequate ab response, he enters equivalence zone; all available ag is complexed with ab, and neither free ag nor free ab can be detected in serum (zone of equivalence)
3. Infection is resolved, patient enters ab excess zone

Question 6

Describe polyclonal antiserum.

Answer 6

It is generally produced in an individual naturally and represents many different clones of B cells that are making ab to many different epitopes on an ag; therefore a heterogenous complex mixture of ab is produced

Question 7

Describe monoclonal ab.

Answer 7

produced by one clone of B cells with specificity for the exact same epitope on an ag. They are produced in the lab

Question 8

Compare and contrast direct vs indirect serologic testing.

Answer 8

Direct serologic testing utilizes a known antiserum in order to detect an unknown ag, either foreign or self (they are qualitative and provide results relatively quickly)

Indirect serologic tests utilize ab from the patient that may be specific for either self or foreign ag (may be qualitative or quantitative)

Question 9

Which is more specific owing to fewer false-positives? Direct or indirect serologic test?

Answer 9

indirect tests

Question 10

Describe agglutination test.

Answer 10

a variation on precipitation reactions.

Ag is a particulate ag such as RBCs or latex beads. Both will clump up to form a lattice of ab-bound particles in the presences of appropriate ab.

Question 11

What are latex bead agglutination tests available for the diagnosis of?

Answer 11

cerebrospinal infections such as Haemophilus, pneumococcus, meningococcus, and Cryptococcus

Question 12

RBC agglutination reactions are important in what cases?

Answer 12

defining ABO blood groups, diagnosing EBV infection (the monospot test), and identifying Coombs test for Rh incompatibility

Question 13

Direct Coombs test

Answer 13

designed to identify maternal anti-Rh ab that are already bound to infant RBCs or antibodies bound to RBCs in patients with autoimmune hemolytic anemia

Question 14

Indirect Coombs test.

Answer 14

designed to identify Rh- negative mothers who are producing anti Rh ab of the IgG isotype, which may be transferred across the placenta harming Rh- positive fetuses.

Question 15

What type of graft rejection is caused by ABO incomaptibility?

Answer 15

hyperacute

Question 16

Describe what the ABO blood groups are?

Answer 16

group of glycoprotein molecules expressed on the surface of erythrocytes and endothelial cells

Question 17

DFA stands for what?

Answer 17

direct fluorescent antibody test

Question 18

What is DFA used for?

Answer 18

used to detect and localize ag in the patient

Question 19

How is DFA used?

Answer 19

tissue sample is treated with ab against that particular ag that have been labeled with a fluorescent dye.

If ag is present in the tissues, the fluorescent-labeled ab will bind, and their binding can be detected with a microscope

Question 20

What does IFA stand for?

Answer 20

indirect fluorescent antibody test

Question 21

How is IFA used?

Answer 21

to detect pathogen-specific ab in the patient

Question 22

Describe the steps in utilization of IFA? Example of main use of this diagnostic tool?

Answer 22

a laboratory-generated sample of infected tissue is mixed with serum from the patient. A fluorescent labeled anti-immunoglobulin is then added.

If binding of ab from patient to the tissue sample occurs, then the fluorescent ab can be bound and detected by microscopy.

can be used to detect autoantibodies in autoimmune diseases

Question 23

ELISA stands for what?

Answer 23

enzyme linked immunosorbent assay

Question 24

How is ELISA performed for HIV testing?

Answer 24

ELISA is used with the p24 capsid ag you insert onto microtiter plates.

The serum from the patient is then added followed by addition of an enzyme labeled antihuman immunoglobulin.

Finally the chromogenic substrate is added and the production of a color change in the well can be observed

Question 25

Anti-human immunoglobulin is added from a rabbit to a test tube which contains a newborn’s RhD+ RBCs covered with maternal anti-Rh antibodies; the result agglutinates the newborn’s red cells. This is an example of which of the following?

A. ELISA test
B. Latex bead agglutination test
C. Direct Coombs test
D. Indirect Coombs test
E. Direct fluorescent antibody test

Answer 25

C. Direct Coombs test

Question 26

What does FACS stand for?

Answer 26

fluorescence activated cell sorting

Question 27

How is FACS performed?

Answer 27

by using ab against cell-surface markers conjugated to different fluorescent dyes, it is possible to analyze the relative numbers of cells present in a specific tissue location

Question 28

Be able to decipher what these different flow cytometric analysis charts mean.

Answer 28

last chart switch 2 and 3