Lewis System

Question 1

Five characteristics of the Lewis System

Answer 1

It is a system, not a blood group antigen
Cord bloods are always Le(a-b-)
Not manufactured by RBC, not integral, adsorbed onto RBC’s
Decreased expression often seen in pregnant women
Leb expression and immunity are affected by phenotype

Question 2

What chromosome is Le gene located on?

Answer 2

Chromosome 19 - short arm
FUT3 gene
FUT1 and FUT2 are closely linked on long arm

Question 3

What does the Le gene code for?

Answer 3

L-fucosyltransferase adds fucose to GlcNAc on type I chains in a 1-4.
Can’t add to type II chains because a1-4 is taken

Question 4

How is Lea formed?

Answer 4

Lea is formed when a fucose is added to type 1 precursor chains
Only Lea is formed when no Se gene present

Question 5

How is Leb formed?

Answer 5

Leb is formed when a fucose is added to Type 1 H chains
Se gene forms H substance
Lea is still present but much less than Leb

Question 6

How is ALeb and BLeb formed?

Answer 6

Se gene forms H substance, A/B genes form A and B substance, Le gene adds fucose > ALeb and BLeb
In group A, most Leb is ALeb

Question 7

What is Lewis antigen carried on in plasma?

Answer 7

Oligosacchride bound to a lipid

Question 8

What is Lewis antigen carried on in Saliva?

Answer 8

Oligosacchride bound to a protein

Question 9

Frequency of Le(a-b+)

Answer 9

72%

80% are secretors

Question 10

Frequency of Le(a+b-)

Answer 10

22%

20% are non-secretors

Question 11

Frequency of Le(a-b-)

Answer 11

30% of blacks lack the Le gene

6% of whites lack Le gene

Question 12

Frequency of Le(a+b+)

Answer 12

16.8% of japenese are Se(w)
also seen in Australian, Chinese, Taiwan, and Polynesians
Se enzyme is ineffective at making H substance to increased Lea antigen

Question 13

Antigen charactersitics

Answer 13

Not expressed on cord cells
Weaken during pregnancy > Esp Group A women
Resistant to most chemicals
Enhanced by enzymes

Question 14

Leb is a receptor for…

Answer 14

H. pylori - bacteria responsible for causing gastritis

Question 15

What is Le(a-b-) associated with?

Answer 15

Increased susceptibility to E. Coli, candida, Cardiovascular disease, and possibly graft failure in renal transplant patients

Question 16

Group A Secretors

Answer 16

May type as Le(a-b-) because all of Leb is ALeb

Question 17

What is Le(abx) antigen?

Answer 17

Also called Stage specific embryonic antigen

Carried on fucosylated unbranched type II chains

Question 18

What is Le(abx) antibody?

Answer 18

Reacts with all cells except le(a-b-) red cells
Reacts with 90% of cord cells (infants with Le gene)
Reacting with type 2 precursor w/ Le fucose
Common and found with anti-Lea and Leb

Question 19

What are Le(x) and Le(y) antigens?

Answer 19

Isomers of Lea and Leb on Type II chains
Not on RBC + Not part of Lewis
Fucose + Type II precursor chain = Lex
Fucose + Type II H chain = Ley
Fucose + H chain + A = ALey
Fucose + H chain + B = BLey

Question 20

Le(c) genetics and antibody

Answer 20

lele, sese
Anti-Le(c) is antibody to precursor type 1 chain or Le(a-b-) non-secretors
adsorbed onto RBC

Question 21

Le(d) genetics and antibody

Answer 21

lele, Se
Le(d) = Type 1 H chains
Anti-Le(d) only reacts with Le(a-b-) secretors or Type I H chains

Question 22

ALe(b)

Answer 22

FUT3 adds fucose to A substance
Anti-ALeb reacts with A positive secretors Le(a-b+)
Can’t be seperated into Anti-A and Anti-Le(b)
Group A secretor plasma will adsorb out regardless of Lewis type

Question 23

BLe(b)

Answer 23

FUT3 adds fucose to B substance
Anti-BLeb reacts with B positive secretors Le(a-b+)
Group A secretor plasma will adsorb out regardless of Lewis type

Question 24

Diseases associated with loss of Lewis antigens

Answer 24

Infectious mononucleosis
Severe alcoholic cirrhosis
Alcoholic pancreatitis

Question 25

Disease associated with increased Lewis antigens

Answer 25

Fucosidosis

Question 26

Describe Lewis antigen developement

Answer 26

At birth infant is Le(a-b-)
2 months type as Le(a+b-)
transitional period of Le(a+b+)
2-3 years true typing can be determined
5-6 years Lewis antigen fully developed

Question 27

Characteristics of Lewis antibodies

Answer 27

Fragile, weak agglutination
Hemolysis rarely seen in vitro (enzyme treated cells increases)
IgM reacts at RT
Naturally occurring
Not clinically significant cause Le antigens can elute off cells
Anti-Lea and anti-Leb often occur together

Question 28

Anti-Le(bH)

Answer 28

Reacts with O and A2 cells Le(a-b+)

Question 29

Anti-Le(bL)

Answer 29

True anti-Leb

Reacts with all Le(a-b+) cells