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IHO Week 6 - WLB > Immunologic Tests - Diebel > Flashcards

Immunologic Tests - Diebel Flashcards

1
Q

What is a direct agglutination test?

A
  • Combine serum + antibody to test for particular antigen
    • no clumping/aggregation = negative
    • clumping/aggregation = positive
      • see direct results of antibody-antigen complex
    • ABLE TO VISUALIZE A REACTION AFTER THE Fab PORTION OF THE ANTIBODY HAS BOUND AN ANTIGEN
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2
Q

What is passive (indirect) agglutination?

A
  • Specific antibody + Latex beads added to serum
    • ABLE TO VISUALIZE REACTION BECAUSE THE Fc PORTION OF THE ANTIBODY WAS BOUND TO A COLORED LATEX BEAD SO THAT WHEN THE Fab PORTION OF THE ANTIBODY BINDS TO ANTIGEN THE BEADS CLUMP TOGETHER
    • no clumping = negative
    • beads clumping = positive
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3
Q

What are the antibodies binding to in direct agglutination?

A

Directly bind to antigen (if positive test).

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4
Q

What are the antibodies binding to in passive (indirect) agglutination?

A

Bind to latex bead + antigen (if positive).

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5
Q

What are the 6 steps of the Direct (Sandwich) ELISA test?

A
  1. Specific antibodies bound to bottom of plate
  2. Add sample serum (with antigen)
  3. Wash with buffer
  4. Add enzyme tagged antibody
  5. Wash with buffer
  6. Add substrate for tagged antibody
    1. color = positive test
    2. no color = negative test
    3. color change directly linked to the antibody that DIRECTLY recognized the antigen.
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6
Q

What are the 6 steps of the Indirect ELISA Test?

A
  1. Specific antigen bound to plate
  2. Add sample serum (with antibodies)
  3. Wash with buffer
  4. Add anti-IgX antibodies with enzyme tag
  5. Wash with buffer
  6. Add substrate tag
    1. color change = positive test
    2. no color change = negative test
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7
Q

What starts out on the plate in a Direct ELISA Test?

A

antibodies

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8
Q

What starts out on the plate in a Indirect ELISA Test?

A

antigen

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9
Q

What are you detecting in a Direct ELISA test?

A

the presence of a particular suspected antigen in a patient’s serum

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10
Q

What are you detecting in a Indirect ELISA test?

A

the presence of a particular suspected antibody in a patient’s serum

(i.e. looking for the body’s immune response to a particular antigen)

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11
Q

What are you washing away during the washes in a Direct ELISA test?

A

antigen that is not specific to the plated antibody

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12
Q

What are you washing away during the washes in a Indirect ELISA test?

A

antibodies that are not specific to the plated antigen

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13
Q

What does a serodiagnosis indicate if IgM is detected in a patient’s sera collected at the onset of the illness?

A
  • Positive in Newborns:
    • in utero (congenital) infection
  • Positive in Adults:
    • primary OR current infection
  • Negative in Adults:
    • no infection (secondary) OR past infection
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14
Q

What does a serodiagnosis indicate if IgG is detected in a patient’s sera collected 2-6 weeks after onset of the illness?

A
  • Positive:
    • fourfold rise or fall in titer between acute and convalescent sera tested at the same time in the same test system
  • Negative:
    • No current infection or past infection
    • OR patient is immunocompromised and cannot mount a humoral antibody response
    • OR convalescent specimen was collected before increase in IgG
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15
Q

What does a serodiagnosis indicate if IgG is detected in a newborn patient’s sera collected between onset and convalescence (recovery) of the illness?

A
  • Positive in Newborn:
    • maternal antibodies crossed the placenta
  • Negative in Newborn:
    • patient has not been exposed to microorganism
    • OR patient has a congenital or acquired immune deficiency
    • OR specimen was collected before increase in IgG
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16
Q

What does a serodiagnosis indicate if IgG is detected in an adult patient’s sera collected between onset and convalescence (recovery) of the illness?

A
  • Positive in Adult:
    • evidence of infection at some unknown time
      • except in certain cases in which a single high titer is diagnostic (rabies, Legionella, Ehrlichia)
17
Q

What are the 6 steps of the Competitive ELISA Test?

A
  1. Mix sample serum (with antigen) + known amount of antigen-specific antibody
  2. Add specimen-antibody complex serum to antigen-specific coated plate
  3. Wash with buffer (to remove unbound antibody)
  4. Add anti-IgX enzyme-tagged antibody
  5. Wash with buffer
  6. Add substrate for tag
    1. color change = negative test
    2. no color change = positive test
18
Q

What starts out on the plate in a Competitive ELISA Test?

A

antigen

19
Q

What are you detecting in a Competitive ELISA Test?

A

the presence of a particular suspected antigen in a patient’s serum

20
Q

What are you washing away during the washes in a Competitive ELISA test?

A

unbound antibody

& then later

unbound anti-IgX antibody

21
Q

What are you testing for presence of in the Hemagglutination assay with a constant amount of RBCs + decreasing amount of serum in a microtiter plate?

A

Antiviral antibodies

  • (+) presence = induces agglutination of the RBCs
    • lattice structure covers well
  • (-) absence = no agglutination of RBCs
    • button, RBCs sink to bottom of well
22
Q

What are you testing for presence of in the Hemagglutination assay with a constant amount of RBCs + constant antibody + decreasing amount of patient virus in a microtiter plate?

A

Virus/viral particle(s)

  • (+) presence = button (RBCs sink)
    • virus is bound by antibody
  • (-) absence = RBC-antibody lattice
    • no virus present
23
Q

What are you testing for presence of in the Hemagglutination assay with RBC + anti-A/anti-B antibodies?

A

A-antigen/B-antigen

  • used for blood typing
  • (+) presence = clumping
    • type A blood/type B blood
  • (-) absence = no clumping
    • type O
24
Q

What are the functions of the three essential chemical components found in HAT media?

A
  • H: Hypoxanthine
    • rescues GTP
    • important in scavenger pathway for IMP/GMP
    • requires HGPRT
  • A: Aminopterin
    • blocks nucleotide synthesis by blocking DHFR
  • T: Thymidine
    • rescues TTP
  • Form of artificial selection for cells containing working TK (thymidine kinase) and HGPRT

IHO Week 6 - WLB (8 decks)

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