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SBB > MNSs System > Flashcards

MNSs System Flashcards

1
Q

What Chromosome is GYPA and GYPB located on?

A

Chromosome 4

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2
Q

What are the GYPA and GYPB antigen characteristics?

A
  • 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
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3
Q

How many antigen sites are on GYPA?

A

1 million

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4
Q

How many antigen sites are on GYPB?

A

200,000

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5
Q

What are the High prevalent MNS antigens?

A

U, Ena, ‘N’, ENKT, ENEP, ENEH, ENAV, ENDA, ENEV

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6
Q

What is the structure of the carbohydrate chains attached to the MNS amino acids?

A

GalNAc - Gal - NANA or (N-Acetylneuraminic acid)

- NANA

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7
Q

What is the function of GYPA/GYPB structures?

A

GPA-deficient red cells are more resistant to invasion by Plasmodium falciparum merozoites
Sialic acid appears to be essential for adhesion of the parasite to the red cells.

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8
Q

What is the function of GYPA on the membrane?

A

GPA associates with band 3, which affects the expression of Wrb of the DI system

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9
Q

What is the function of GYPB on the membrane?

A

GPB associates with Rh proteins and Rh-associated protein (RHAG).
Rh null cells have reduced S and s. (Serologically weak or negative)

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10
Q

What are the amino acids that code for M?

A

SERINE-Serine-Threonine-Threonine-GLYCINE

Serine/Leucine at position 1 and Glycine/Glutamic Acid at position 5

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11
Q

What are the amino acids that code for N?

A

LEUCINE-Serine-Threonine-Threonine-GLUTAMIC ACID

Serine/Leucine at position 1 and Glycine/Glutamic Acid at position 5

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12
Q

What are the amino acids that code for S and s?

A

LEUCINE-Serine-Threonine-Threonine-GLUTAMIC ACID

amino acid difference for S/s – Methionine/Threonine 48 at position 29

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13
Q

What is ‘N’?

A

The first 5 amino acids on GYPB are the same as N antigen.

If GPYB present will have ‘N’ antigen and people usually don’t make anti-N

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14
Q

What is linkage disequilibrium in the MNS system?

A

MNS inherited as haplotypes: MS, Ms, NS, Ns
S is found twice as often with M than with N
M+, it is likely also S+; a cell that is M-S+ is not as common

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15
Q

What are the general MNS antigen frequencies?

A

M an N are present in approx 75% of whites and blacks
S is present in 50% of whites and 30% of Blacks
s is present 90% of whites and blacks
U negative is present in 1% of blacks

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16
Q

What are the most common MNS haplotypes

A

Ns > Ms > MS > NS

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17
Q

What is the effect of ficin/papain to MNSs antigens?

A

MN is destroyed

Ss are variable and less effected because S and s are further down the polypeptide and less accessible

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18
Q

What is the chlorine on S antigens?

A

Destroyed

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19
Q

What is the effect of Trypsin on MNSs antigens>

A

MN is destroyed

Ss are resistant

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20
Q

What is the effect of chymotrypsin?

A

MN is resistant

Ss are destroyed

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21
Q

What is the effect of DTT on MNSs antigens?

A

MNSs are not destroyed by DTT

MN are destroyed by ZZAP

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22
Q

What is effect of nueraminidase?

A

treating cells with nueraminidase will cleave the sialic acid residues and destroys antibody reactivity only in some antibody

23
Q

What are characteristics of anti-M?

A

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

24
Q

What are the characteristics of anti-N?

A

Naturally occurring
IgM; rarely IgG
Not common because of ‘N’ present in most people
Anti-N not reacting at 37C is not clinically significant

25
Q

What are the characteristics of anti-S?

A

Can be naturally occurring
IgG
Can cause HDFN and TRN RXN
Can be enhance my incubating at room temp

26
Q

What are the characteristics of anti-s?

A

IgG
Can cause HFN and TRN RXN
May be enhanced by lowering pH to 6.0

27
Q

What can make clinically significant anti-N

A

M+N-S-s- U- lack GPYB so no ‘N’

28
Q

What is Glycine Soya?

A

Ficin control that reacts with all cells that reduced sialic acid residues
Can be used to screen for U- donors because S-s-U- cells have reduced sialic acid

29
Q

How does allo anti-M form in M+ people?

A

antibody is directed to a portion of M not present on patients own cells
auto and DAT are negative
Usually reacts at RT or 4C

30
Q

What is anti-Nf

A

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.

31
Q

What is anti-N lectin?

A

Nvg - made from the lectin Vicia graminea, which has anti-N specificity when diluted appropriately
When not diluted will react with GYPB - ‘N’

32
Q

Why doesn’t anti-N reagents react with ‘N’

A

GYPB is less abundant on RBC’s

33
Q

What cells have more ‘N’?

A

S SGP is 1.5x more prevalent on the red cell than s SGP. Therefore, S+ rbcs have more ‘N’ than S-s+ rbcs.
U neg cells (lack GPB) also lack ‘N’.

34
Q

That is the effect of enzymes to ‘N’?

A

Destroyed by Papain/ficin like M and N
Resistant to trypsin
Destroyed by chymotrypsin

35
Q

What is anti-GPB?

A

Antibody that can be made by N- U- individuals

36
Q

What is Ena?

A 
High freq present on GYPA
Rare deletion results in M- N- Ena- Wrb -phenotype
Reduced sialic acid residue
Glycine Soya will be positive in Ena-
Present on cords
DTT resisant
37
Q

Anti-EnaTS

A

Trypsin Senstive - does not react with En(a+) cells treated with trypsin, ficin or papain.

38
Q

Anti-EnaFS

A

Ficin sensitive - represents those Ena antibodies that recognize a ficin-sensitive (papain sensitive, trypsin resistant) determinant

39
Q

Anti-EnaFR

A

Ficin resistant - represents those antibodies that react with a ficin-resistant (papain resistant, trypsin-resistant) determinant

40
Q

Anti-Ena characteristics?

A

IgM or IgG seen at IAT
Can cause TXN RXN or HDFN (Transfuse Ena- units)
Can be an autoantibody
Ena neg individuals who make anti-Ena often make anti-Wrb (Ena required for Wrb expression)
Anti-Ena is directed against different portions of GPr
Extremely difficult to find Ena- blood. Look at siblings

41
Q

U antigen Characteristics

A

Resistant to all chemicals
U negative found in 1% of blacks
U antigen is present on cord cells

42
Q

Anti-U characteristics?

A

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)

43
Q

What is Uvar?

A 
16% of serological S-s- have U var 
Uvar is a hybrid gene
Weak U antigen is detected absorption and elution
23% are He+
Can make anti-U
44
Q

What is MkMk phenotype?

A

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-)
Heterzygous = Cells will express MNS antigens produced by the normal allele
-For example, Mk/Ns will type M-N+S-s+.

45
Q

Mc

A

Single amino acid change in GYPA produces low frequency antigen
Intermediate between M and N antigens.
Reacts with most anti-M and some rabbit anti-N, but negative with Nvg lectin.
Often present with M1 antigen (see MN CHO section)

46
Q

Mg

A

Single amino acid change in GYPA produces low frequency antigen
Found more often among Swiss.
Previously used as an adjunct in paternity testing.
Anti-Mg is common. Antibody can be made in rabbits.

47
Q

He (Henshaw)

A

Single amino acid change in GYPB produces low frequency antigen
Antithetical to ‘N’ – He positive cells do not express ‘N’
Positive in 23% Uvar

48
Q

Dantu and Sta

A

Dantu is found in blacks
Sta is found in very low frequency, but seen in Japanese and Asians
These are hybrid antigens
Carry a protease resistant N which is probably ‘N’
Ficin-treated cells will react with Nvg lectin
Anti-Dantu may be found in reagent anti-S

49
Q

What is Mur?

A

Rare in European and African ethnicity, but higher prevalence in Chinese (7%) and Thais (10%)
Form of Hybrid of GPYB
Anti-Mur causes HTR/HDFN and is the most common blood group antibody after anti-A/-B in Hong Kong and Taiwan.
Screen cells used in Southeast Asian labs should include a Mur+ cell.

50
Q

MN CHO Blood Group Collection

A 
Abnormal glycosylation (sialic acid or GluNAc) on GPA resulted in 6 antigens, now grouped in a separate blood group collection called MN CHO
Antigens: M1, Hu, Tm, Can, Sext, Sj
51
Q

What is M1?

A

Low prevalence (0.5% W, 16.5% B), found only on M+ cells, but is not an enhanced M
Anti- M1 made primarily by M- (and some M+N+) individuals
Anti-M and anti- M1 are not the same. Some anti-M react only with M1+ cells
Amino acids are same in M and M1 but there is abnormal glycosylation
GlcNAc is substituted for NANA on 1st GlcNAc
This in inhibits glycosylation of amino acids 3 and 4

52
Q

What is Tm?

A

Amino acids 1-5 look like N

Like M1 there is a GlcNAc substituted for the 1st NANA which inhibits glycosylation of amino acids 3 and 4

53
Q

What is T and Tn?

A

Abnormal glycosylation results in polyagglutination
T is when both NANA are removed and just GalNAc-Gal are present
Tn is where the terminal NANA and GAL are removed exposing the GalNAc
Reacts with human anti-A

SBB (37 decks)

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