Immunology CH 3.2 Immunologic Procedures

Question 1

The interaction between individual antigen and antibody molecules depends on several types of bonds such as ionic, hydrogen, hydrophobic, va der waals forces. How is the strength of this attraction characterized?

Avidity
affinity
reactivity
valency

Answer 1

Affinity refers to the strength of a single antibody antigen interaction

avidity is the strength of multiple interactions

Question 2

A lab is evaluating an ELISA for detecting CCp markers in rheumatoid arthritis. The lab includes serum from healthy volunteers and from patients with other connective tissue diseases in the eval. These specimens deterine which factor of the assay?

sensitivity
precision
bias
specificity

Answer 2

specificity, a negative result in the absence of a disease

Question 3

the detection of precipitation rxn depends on the presence of optimal proportions of antigen and antibody. a patients sample contains large amound of antibody, but the reaction in a test system containing antigen is negative. What has happened?

preformance error
low specificity
a shift in the zone of equivalence
prozone phenomenon

Answer 3

prozone phenomenon, excess antibody

Question 4

the positive and negative control values for an ELISA procedure are below their accebtable ranges. What is most likely the cause?

decay of postive and negative controls
incomplete washing following specimen addition
overly long incubation times
decay of antibody enzyme conjugate

Answer 4

antibody enzyme conjugate is sensitve to storage and easy to dissasosiate

Question 5

what is the interpretation when an ouchterlony plate shows crossed lines between wells 1 and 2 (antigen is placed in the center well and antisera in wells 1 and 2)

no rxn between wells 1 and 2
partial identity between wells 1 and 2
nonidentity between wells 1 and 2
identity between wells 1 and 2

Answer 5

crossed lines mean non identity

Question 6

a weight lifter taking many suppliments is tested for TSH, in a direct capture assay, using spretavidinbiotin indicator. She has normal TSH levels for the past 3 months on specimens collected in late evening. This month she comes in right after breakfast for her blood draw, the TSH level is three times her previous level. What may be causing this?

diurnal variation in TSH levels
exogenous biotin in her system from a suppliment taken that morning
reduced thyroid function caused by an unknown pathology
pipetting error

Answer 6

high levels of exogenous biotin

Question 7

what compromises the indicator system in an indirect ELISA for detecting antibody?

enzyme conjugated antibody + chromo substrate

enzyme conjg antigen + chrom subst

enzyme + antigen

substrate + antigen

Answer 7

enzyme conjugated antibody and chromogenic substrate

Question 8

what outcome results from improper washing of a tube or well after adding the enzyme antibody conjugate in an ELISA system?

result will be fasely decreased
result will be fasely increased
result unaffected
result is impossible to determine

Answer 8

false increased result

Question 9

what would happen if the color reaction phase is prolonged in one tube or well of an ELISA test?

result will be false decrease
result will be false increase
result unaffected
impossible to determine

Answer 9

false increased/elevated result

Question 10

the absorbance of a sample measured by ELISA is greater than the highest standard. what corrective action should be taken?

extrapolate an estimated value from the higher reading
repeat the test using a standard of higher concentration
repeat the assay using one half of the volume sample
dilute the sample

Answer 10

dilute the sample and test again

Question 11

a pt is suspected of having a lymphoproliferative disorder. after several tests were completed, the patient was found to have an IgMk paraprotein. In what sequence should the lab tests leading to this diagnosis have been preformed?

serum electrophoresis (SPE) followed by immunofixation electro (IFE)
Ig levels followed by SPE
total lymph count followed by Ig levels
Ig levels followed by electrophoresis (urine)

Answer 11

A, SPE followed by IFE

Question 12

an IFE preformed on a serum sample showed a narrow dark band in the lanes containing anti-y and anti-lambda. How should this be interpreted?

abn decreased IgG concentration
abn test result demonstrating monoclonal IgGlambda
normal results
impossible to determine

Answer 12

B, monoclonal IgG lambda

Question 13

which type of nephelomtery is used to measure immune compex formation almost immediately after reagent has been added?

rate
endpoint
continuous
one-dimensional

Answer 13

rate

Question 14

A ANA test was preformed using IFA, and clincally signficiant patterns were reported. postive and negative controls are good. However, the clinical eval of the pt was not consistent with the pattern reported. What is the most likely explanation?

the clinical condition of the pt changed since the sample was tested
the pattern of fluorescence was misinterpreted
the controls were misinterpreted
the wrong cell line was used for the test

Answer 14

B, the fluorescene was misinterpreted

Question 15

what corrective action should be taken when a specific pattern cannot be IDd in a specimen with a positive ANA IFA?

repeat testing with a larger volume
call the physician
have another tech read the slide
dilute the sample and retest

Answer 15

dilute the sample and retest

Question 16

which statement best describes passive agglutination reactions used for serodiagnosis

such agglutination rxn are more rapid because they are single step processes
reactions require the addition of a second antibody
passive agglutination requires biphasic incubtion
carrier particles for antigen such as latex are used

Answer 16

carrier particles like latex are used

Question 17

what has happened in a titer, if tube nos 5 to 7 show a stronger reaction than tube Nos 1 to 4?

prozone reaction
postzone reaction
equivalence reaction
poor technique

Answer 17

A prozone reaction,excess antibody saturated the binding sites

Question 18

what is the titer in tube No. 8 if tube I is undiluted and dilutions are doubled?

64
128
256
512

Answer 18

128, 2^7

Question 19

the directions for a slide agglut test instruct that after mixing the pt serum and antigen coated latex particles, the slide must be rotated for 2 min. What would happen if the slide was rotated for 10 minutes?

false pos result
false neg result
no effect
depends on the amount of antibody in the sample

Answer 19

false positive reading

Question 20

which outcome indicates a negative result in a complement fixation test?

hemagglutination
absence of hemagglugtination
hemolysis
absence of hemolysis

Answer 20

hemolysis indicates a negative result in compliment fixation

Question 21

what effect does selecting the wrong gate have on the results when cells are counted by flow cytometry?

no effect
failure to count the desired cell popuation
false elevated results
impossible to determine

Answer 21

failure to count the desired cell population

Question 22

which statement best describes immunophenotyping?

lineage determination by detecting antigens on the surface of the gated cells by using flurorent abs

ID of cell maturity by using antibody to detect antigen within the nucleus

ID and sorting of cells by front and side scatter of light from a laser

analysis of cells collected by flow cytometry using tradition agglut reactions

Answer 22

A lineage determination by detecting antigens on the surface of gated cells using fluorescnece

Question 23

a flow cytometry scattergram of a bone marrow sample shows a dense population of cells located inbetween normal lymph and normal myeloid cells. what is the most likely explanation?

sample is improperly collected
an abn cell population is present
the laser optics are out of alignment
the cells are most likely not leukocytes

Answer 23

abn cell population is present