Immunology in Infection and Diagnosis

Question 1

How can you diagnose HIV?

Answer 1

via ELISA
Western Blot
PCR
Flow Cytometry

Question 2

What three antigens do you need to diagnosis HIV on a western blot

Answer 2

gp120
gp41
p24
(P17-> matrix antigen is also often detected)

Question 3

If you want to see if someone is infected what do you look for? If you want to see if someone has ever been infected, what do you look for?

Answer 3

IgM

IgG

Question 4

What are the general principes for immunoassays?

Answer 4

decide if you want to measure antigen or antibody
decide upon system of detection
notice how antigen-antibody complexes are separated
establish controls, positive, and negative

Question 5

Only (blank) anti-HIV will be diagnostic for infection of the baby

Answer 5

IgM

Question 6

Maternal (blank) anti-HIV will cross the placenta and persist for months

Answer 6

IgG

Question 7

At what age do babies lack all maternal antibody and has to start making its own?

Answer 7

6-9 months

Question 8

How does an ELISA work?

Answer 8

antigens are stuck onto a plastic surface, a sample is added and any antibodies for the disease we are testing for will bind to the antigens. Next a second antibody with a marker is added and a positive reaction is detected by the marker changing colour when an appropriate substrate is added. If there are no antibodies in the sample, the second antibody will not be able to stick and there will be no colour change.

Question 9

What is a sandwich ELISA?

Answer 9

For an antigen ELISA, antibodies are bound to a plastic surface, a sample is added and if antigens from the virus we are testing for are present they will stick to the antibodies. This test then proceeds in the same way as the antibody ELISA

Question 10

When do you use ELISAs?

Answer 10

for detection of IgG, IgM,

Question 11

What would you want to detect IgM for?

Answer 11

current infections such as H. pylori, EBV, Rotavirus

Question 12

What is this:

True positives/ (true positives + false positives)

Answer 12

sensitivity

Question 13

What is this

False positive/ (true positive + false positive)

Answer 13

specificity

Question 14

Is the P24 EIA a sensitive and specific test for HIV

Answer 14

yes!!! 100% sensitive and 99.75% specific

Question 15

How does a western blot work to find HIV?

Answer 15

multiple Ag proteins (virus and cell protein)
use SDS to give proteins negative charge.
utilize electrophoresis.-> proteins are stained -> proteins are blotted from gel onto filter paper-> human serum is added -> enzyme conjugated goat antibody to IgM is added and use to detect bound (human) antibody-> bands of insoluble product from substrate indicate where ab’s have been bound to different HIV ag’s

Question 16

On western blot, what do you need to have to prove that someone is HIV positive?

Answer 16

minimum of 2 of 3 major HIV proteins (P24, Gp41, Gp120/Gp160)

Question 17

When are western blots used?

Answer 17

when the stakes are high for a correct diagnosis

e.g HIV, Hep C, lyme diseae

Question 18

How can you use flow cytometry to detect AIDS? How?

Answer 18

you look at the CD4 T cells to see if there is depletion. Take mouse anti-CD4 and CD8 which are coupled with flouresecents

Question 19

What color will a CD8 T cell flouresce?

Answer 19

red

Question 20

What color will a CD4 T cell flouresce?

Answer 20

green

Question 21

How does flow cytometry work

Answer 21

you put markers on cels and thne place them in a single file stream to be excited by lazors and separated out based on color that fluoresces

Question 22

Besides CD4 T cells what else can HIV infect?

Answer 22

monocytes and macrophages

Question 23

CD4 Ts below (blank) =AIDS

Answer 23

200 per microliter

Question 24

In AIDs, CD4 Ts decrease and C8 Ts stay constant for a long time. What is the normal ratio of CD4:CD8?

Answer 24

2 to 1

Question 25

What are the unstained cells for in flow cytometry?

Answer 25

they are your negative controls

Question 26

Flow cytometry is often expressed how?

Answer 26

in a histogram

Question 27

What is the MFI?

Answer 27

median fluorescent intensity and it is used to describe the extent to which cells are labeled with antibodies

Question 28

What are some clinical applications of flow cytometry in medicine?

Answer 28

identify T and B leukemias
monitor CD 4 T cells in AID
check for immunlogical changes in diseases, such as NK cells in Chronic fatigue syndrome

Question 29

What is FITC?

What is PE?

Answer 29

IgD

IgM