Immune response as a function of time

Question 1

What makes RBCs very immunogenic?

Answer 1

they are heavily glycosylated

Question 2

What does 2-ME do to Ab.s?

Answer 2

reducing agent (reduces disulphide bonds) and inhibits the activity of IgG

Question 3

What effect does heating serum have?

Answer 3

deactivates complement proteins

Question 4

Describe the differences between IgM and IgG (-mers, number of Ag binding site, fixes complements, Fc binding, crosses the placenta, biological functions)

Answer 4

IgM:
- pentamer
- 10 Ag binding sites
- does not cross the placenta (too big)
- fixes complement
- Fc does not have any FcRs
- bio functions = produced at first response to Ag, BCR

IgG:
- monomer
- 2 Ag binding sites
- crosses the placenta
- fixes complement
- Fc binds to phagocytes
- bio functions = long-term immunity, memory Abs, neutralizes toxins, opsonization

Question 5

Describe four different Ab functions and what they do/allow?

Answer 5

1. complement fixation –> lyse bacteria by forming a MAC complex
2. opsonization –> enhance recognition + easier to engulf
3. neutralization –> blocks virulence factors (e.g. toxins)
4. agglutination –> allows bacteria to be more easily recognized when filtered so they can be removed + prevents bacteria from entering cells

Question 6

How was hemagglutination and hemolysis first observed?

Answer 6

during early attempts to perform blood transfusions: gave SRBCs to humans (xenogenic transplantation) –> not very compatible

Question 7

Why would be perform both hemaglutination and hemalysis assays?

Answer 7

one may be more sensitive than the other

Question 8

Describe how the hemagglutination assay works using SRBCs

Answer 8

• in the absence of anti-SRBC Abs, the SRBCs will settle to form a button
• in the presence of anti-SRBC Abs, the SRBCs will form a cross-linked network that inhibits gravity-induced settling –> creates a net/haze

Question 9

Describe how we can use a hemagglutination assay to determine blood type

Answer 9

take patient blood –> add anti-A to one well, add anti-B to one well –> if only anti-A results in hemagglutination = type B; if only anti-B results in hemagglutination = type A; if both anti-A and -B result in hemagglutination = type AB; if neither anti-A or -B result in hemagglutination = type O

Question 10

Describe the direct coomb’s test. What can it test for?

Answer 10

1. blood sample is taken from patient with Ab.s or virus attatched to RBCs
2. add coomb’s reagent (anti-human or anti-viral)
3. aggluntination reaction is visible after cross-linking of Abs

test = hemolytic anemia; tranfusion reactions; viruses

Question 11

Describe the indirect coomb’s test. What can it test for?

Answer 11

1. patients serum with Abs is drawn
2. donor blood is added
3. patients Ab’s bind to donor’s RBCs
4. Coomb’s reagent is added
5. aggluntination

test for = mothers Abs vs newborn RBCs and blood compatibility before transfusions

Question 12

what is a serial dilution?

Answer 12

each successive dilution is derived from the previous

Question 13

what is a titre?

Answer 13

corresponds to the most dilute concentration at which the desire effect is still seen

Question 14

Describe both a postive and negative hemolysis test when testing for prior bacteria infection

Answer 14

positive test:
1. Ag and complement are added to serum with Ab against Ag
2. complement fixation
3. add SRBC and Ab to SRBC
4. no hemalysis (complement tied up in Ag-Ab rxn)

negative test:
1. Ag and complement are added to serum without Ab against Ag
2. no complement fixation
3. add SRBC and Ab to SRBC
4. hemalysis (uncombined complement available)