Immunology

Question 1

T Helper Cell / Phenotypic Markers / MHC / Fxn

Answer 1

CD3 (TCR)
CD4
MHC Class II restricted activation (antigen presentation)
Cytokine production –> T & B cell differentiation, macrophage activation

Question 2

Cytotoxic T Cell / Phenotypic Markers / MHC / Fxn

Answer 2

CD3 (TCR)
CD8
MHC Class I restricted activation (virus or tumor infected cells; allograft cells)
Cell lysis

Question 3

B Cell / Phenotypic Markers / MHC / Fxn

Answer 3

CD19/CD21 (BCR)
MHC I and II
Antibody production

Question 4

MHC I vs II: expression on which cells; interacts with?

Answer 4

Class I: expressed on all nucleated cells (interacts with cytotoxic t cells)
Class II: expressed on APCs (interacts with T helper cells)

Question 5

Costimulatory: CD28 - CD80/86 (which cells; interaction?)

Answer 5

CD28 = T cell
CD80/86 (B7) = APC

Mobilizes kinases, cytokine production, T cell proliferation

Question 6

Costimulatory: CD40 - CD40L (which cells; interaction?)

Answer 6

CD40L = T cell
CD40 = APC

B cell proliferation, Ab class switching, memory cell formation

Question 7

Costimulatory inhibitor that binds to CD80/86

Answer 7

CTLA4 (greater affinity for CD80/86 vs CD28)

Question 8

What is Luminex Single Antigen Bead (SAB) test? What does it tell you?

Answer 8

What: synthetic beads are coated with HLA antigens & mixed with recipient serum —> detects anti-HLA antibodies
Info: Class I and Class II HLA antibodies (detect DSA, cPRA)

Question 9

What is the C1q Assay? What does it tell you?

Answer 9

Modified Luminex SAB to only identify DSA that bind C1q (first part of complement activation)

Question 10

What is the CDC Crossmatch? What does it tell you?

Answer 10

Donor lymphocytes + recipient serum + complement [if +DSA –> lymphocytic lysis]
Info: T-cell crossmatch (Class I HLA), B-cell crossmatch (Class I & Class II HLA)
Will also detect non-HLA antibodies

Question 11

What is the Flow Crossmatch? What does it tell you?

Answer 11

Donor lymphocytes + recipient serum + fluorescein-labeled antibodies against IgG [if +DSA –> antibody binds]
Info: T-cell crossmatch (Class I HLA), B-cell crossmatch (Class I & Class II HLA).

Question 12

What is DTT treatment.

Answer 12

DTT reduces the disulfide bonds in IgM thereby preventing IgM antibodies from generating a positive result –> rule out autoantibodies from recipient

(+) CDC, (+) DTT: DSA

(+) CDC, (-) DTT: IgM antibodies are generally not considered to be real sensitization

Question 13

Flow vs CDC Crossmatch : which is more sensitive?

Answer 13

Sensitive: Flow XM

Question 14

What is pronase treatment

Answer 14

Reduce background reactivity in B-cell FC XM d/t nonspecific Ig binding by Fc receptors and surface Ig

Pronase = proteolytic enzyme that can remove Fc receptors from a cell surface

Question 15

How to monitor DSA post-txp in patients high risk for AMR?

Where high-risk = req desensitization or (+) DSA with (-) XM

Answer 15

DSA screen and biopsy within 3 months of txp

Question 16

How to monitor DSA post-txp in patients intermediate risk for AMR?
Where intermediate-risk = hx sensitization but currently negative

Answer 16

DSA screen within 1st month, if (+), do biopsy

Question 17

How to monitor DSA post-txp in patients low risk for AMR?

Answer 17

DSA at least once within 3 - 12 months post-txp or if needed for-cause

Question 18

When should DSA be checked in patients >1 year post-txp

Answer 18

• Signif. change to ISN
• Nonadherence
• Graft dysfunction
• Transfer of care