MNS Flashcards
GYPA and GYPB location
Chromosome 4q31.21
glycophorin A expressed on
erythroid cells only
GPA and GPB are exploited by which parasite
Plasmodium falciparum
How many copies per RBC
GPA
10^6
How many copies per RBC
GPB
200,000
M/N located on
GPA
S/s located on
GPB
‘N’
N like epitope present on GPB- usually too weak to be detected by most reagents
M and N are trypsin
sensitive
S and s are trypsin
resistant
M, N, S, s reactivity with a-chmyotrypsin
M and N- activity partially reduced
S, s, ‘N’- completely destroyed
M, N, S, s reactivity with papain
destroyed
M, N, S, s reactivity with ficin
destroyed
M, N, S, s reactivity with bromelin
destroyed
M, N, S, s reactivity with pronase
destroyed
Frequency M+N-
White: 30%
African American: 25%
Frequency M+N+
White: 49%
African American: 49%
Frequency M-N+
White: 21%
African American: 26%
Frequency S+s-
White: 10%
African American: 6%
Frequency S+s+
White: 42%
African American: 24%
Frequency S-s+
White: 48%
African American: 68%
Frequency S-s-
White:0%
African American: 2%
What are the GYPA and GYPB antigen characteristics?
- Single pass glycoprotein
- AKA sialoglycoprotein
- Glycosylated = sugar attached to an amino acid
- 60% of RBC membrane carbohydrate (sialic acid)
- Accounting for 80% of the net negative charge
- 2-4% of the membrane protein
What is the function of GPA on the membrane?
GPA associates with band 3, which affects the expression of Wrb of the DI system
What is the function of GPB on the membrane?
GPB associates with Rh proteins and Rh-associated protein (RHAG).
Rh null cells have reduced S and s. (Serologically weak or negative)
What are the most common MNS haplotypes
Ns > Ms > MS > NS
What are characteristics of anti-M?
Naturally occurring
Seen in children with bacterial infections
IgM; 50% will have IgG
May be enhanced by lowering pH
Anti-M not reacting at 37C is not clinically significant
What are the characteristics of anti-N?
Naturally occurring
IgM; rarely IgG
Not common because of ‘N’ present in most people
Anti-N not reacting at 37C is not clinically significant
What are the characteristics of anti-S?
Can be naturally occurring
IgG
Can cause HDFN and TRN RXN
Can be enhance my incubating at room temp
What are the characteristics of anti-s?
IgG
Can cause HFN and TRN RXN
May be enhanced by lowering pH to 6.0
What is anti-Nf
RT, rarely 37
Not clinically significant for transfusion
Rare antibody found in patients (N+ or N-) dialyzed with equipment cleaned with formaldehyde
Trace formaldehyde can chemically modify the M and N antigens on the patient’s blood that goes through the dialysis equipment.
What is anti-N lectin?
Nvg - made from the lectin Vicia graminea, which has anti-N specificity when diluted appropriately
When not diluted will react with GYPB - ‘N’
Anti-U characteristics?
IgG reacts at IAT
Can cause TXN RXN and HDFN
Can be auto antibody
Most commonly found in blacks
Not all Anti-U are compatible with U negative RBC’s (seen in U variants)
Some can tolerate blood from Uvar donors
Patients who are also N negative can make anti-U and anti-N (Anti-GPB)
What is Uvar?
16% of serological S-s- have U var
Uvar is a hybrid gene
Weak U antigen is detected absorption and elution
Can make anti-U
What is MkMk phenotype?
Extremely rare phenotype (Mk is not a gene)
Caused by GYP*01N allele that produces no GPA or GPB.
Homozygous = Cells are M-N-S-s-U- ‘N’-, En(a-), Wr(a-b-)
He (Henshaw)
Single amino acid change in GYPB produces low frequency antigen
Antithetical to ‘N’ – He positive cells do not express ‘N’
Anti- M/N
HTR/HDFN
Very occasional cause of acute or delayed HTR
Very rare cause of HDFN
Anti-S/s
HTR/HDFN
Have been implicated in HTRs and severe and fatal HDFN
Mur
Low incidence antigen that is a result of cross over between GYPA and GYPB
Mur frequency
Rare in European and African populations
Up to 7% in China and 10% in Thai populations
Anti-Mur
extremely common in Southeast Asia
Causes severe HTRs and HDFN
En^a
Located on glycophorin A
Not destroyed by enzyme treatment
GPA null phenotype lacks what antigens
M-N-Ena-, Wr(a-b-)
GPB lacking null phenotype
S-s-U-
Lacking both GPA and GPB
MkMk
