HLA Antibodies

Question 1

where do HLA antibodies result from?

Answer 1

exposure to non-self HLA antigens (not naturally occurring such as ABO antibodies)

Question 2

the most common exposures to HLA antigens are through:

Answer 2

blood transfusion
pregnancy
previous transplant/tissue

Question 3

Bw4 frequency in Canadian popl’n

Answer 3

73%

Question 4

Bw6 frequency in Canadian popl’n

Answer 4

83%

Question 5

why are HLA Abs important

Answer 5

• need to detect them and define so crossmatch results can be interpreted and predicted
• antibody screening performed on all potential transplant recipients and repeated while they are waiting for transplant
  => must be repeated following any potential immunizing event like transfusions

Question 6

parts of an antigen molecule which contact the Ag binding site of Ab or T-cell receptor

Answer 6

epitope

Question 7

define allo-epitopes

Answer 7

epitopes that differ among individual members of the same species

Question 8

cross-reactive epitopes

Answer 8

HLA Abs that react with more than one gene/allele have shaed cross-reactive epitopes

CREG

Question 9

as a result of this, pts can make multiple Abs from an exposure to one mis-matched antigen

Answer 9

cross-reactivity

Question 10

two types of epitopes relevant to HLA antigens

Answer 10

public - CREG

privae - on one single gene product

Question 11

an example of a public epitope

Answer 11

Bw4/Bw6

Question 12

Bw4 freq in Canadian popln

Answer 12

73%

Question 13

Bw6 freq in Canadian popln

Answer 13

83%

Question 14

shared ____ _____ sequences between antigens can offe protection between mismatches

Answer 14

amino acids

Question 15

T or F. When a donor has HLA-A2 and pt does not, the recipient can only make anti-A2

Answer 15

F! can also make antibodies to antigens that share the same epitope as A2

Question 16

describe HLA crossmatching

Answer 16

• incubation of donor cells with recipient serum/sera
• test determines if there is pre-formed Ab in recipient to donor
• multiple sera samples may be used
• two methods for XM = CDC-AHG, flow cytometry XM
• interpret with review of recipient HLA typing and donor HLA typing and recipient HLA antibody screen

Question 17

once patients are listed on transplant list, what must they do?

Answer 17

provide monthly bloodwork to HLA lab for ongoing HLA Ab screen and samples for XM available at all times

Question 18

HOPE

Answer 18

human organ procurement and exchange
- determines if a potential donor is suitable
- HLA tech on call notified of the donor