Lewis

Question 1

The_________ is unique among blood group systems because these antigens are not part of the red blood cell (RBC) membrane itself.

Instead, the antigens exist in the_____ and passively adsorb onto the RBC membrane from circulating glycolipids.

Answer 1

Lewis blood group system

plasma

Question 2

This means that Lewis antigen expression on RBCs can change depending on an individual’s…(2)

Answer 2

secretor status
plasma composition

Question 3

ISBT symbol

Answer 3

LE

Question 4

ISBT NUMBER

Answer 4

007

Question 5

GENE PRODUCT

Answer 5

Alpha-1-4-L-fucosyltransferase (FUT3)

Question 6

Consists of two antigens:

Answer 6

Le^a
Le^b

Question 7

●
– produced if (+) Le gene

Answer 7

Le^a

Question 8

●
– produced if (+) Le and Se gene

Answer 8

Le^b

Question 9

has the same precursor as ABO Antigen →_______

Answer 9

TYPE 1 paragloboside (found on secretions only)

Question 10

Secretions (4)

Answer 10

Saliva
sweat
tears
breastmilk

Question 11

Genes involved
(Found at Chromosome 19)

Answer 11

Le
Se
H

Question 12

Le

Enzyme

Answer 12

Alpha 1,4-L-fucosyltransferase

Question 13

Se
H

Enzyme

Answer 13

Alpha 1,2-L-fucosyltransferase

Question 14

compete with each other in whoever adds fucose first to the paragloboside

Answer 14

● Le & Se

Question 15

○ If Le adds fucose first =

○ If Se adds fucose first , Le can still add fucose =

Answer 15

Le^a
Le^b

Question 16

ABO and Lewis antigens can coexist b/c they have the same precursor

Answer 16

Type 1 paragloboside

Question 17

● If Le gene is the ONLY PRESENT and adds fucose sugar, it
forms the______

● If BOTH Le gene and Se gene are present, Le^a gene WILL NOT
be produced but the______
● If H gene is the ONLY PRESENT and adds fucose sugar, it forms
______

● If BOTH Le gene and H gene are present,_____ antigen will still
be formed

Answer 17

Le^a phenotype/antigen

Le^b gene

H phenotype/antigen

Le^a

Question 18

Recall that in order to have Le^b gene, presence of_____ and _____ SHOULD be presen

Answer 18

Le gene and Se gene

Question 19

Antigens are resistant to

Answer 19

Ficin
Papain
DTT
Glycine-acid
EDTA

Question 20

Antibody

• Most commonly encountered
• Often IgM; sometimes IgG

Answer 20

ANTI-Le^a

Question 21

Antibody

• Not common and not as reactive
• Does not readily fix complement
• Anti-Le^bL and Anti-Le^bH

Answer 21

ANTI-Le^b

Question 22

Antibody

• Formerly known as anti-Lex
• Agglutinates Le (a+b-) and Le(a-b+)
  cells
• Formed by all Le(a-b-)

Answer 22

ANTI - Le^ab

Question 23

– present in the secretions, plasma and other tissues; B1→3 linkage

Answer 23

TYPE 1

Question 24

– present in RBCs; B1-4 linkage

Answer 24

TYPE 2

Question 25

_____enzyme adds fucose specifically to the 4th carbon of GlcNac.

Answer 25

FUT3

Question 26

are amorph ○ They do not encode for any transferase enzyme; no antigen expression

Answer 26

se and le

Question 27

***Transfers L-fucose to the 4th carbon of GIcNAc of the type 1 chain*** and forms Le^a Is in intimate association with Se and ABH genes in the formation of Leb

Answer 27

Alpha-4-L-fucosyltransferase

Question 28

antigen is consistently found in the plasma of individuals, irrespective of their secretor status.

Answer 28

Le^a

Question 29

Formation of Lea Antigen • The Lewis (Le) gene encodes the enzyme α-1,3/4-fucosyltransferase, which adds____ to the type 1 precursor chain (found in body fluids). • When only the Le gene is present, the____ antigen is produced. • However, since this antigen forms in secretions first and is then absorbed onto RBCs, Le(a+) individuals are usually ABH non-secretors (sese).

Answer 29

fucose Lea

Question 30

Formation of Leb Antigen • If both the Le and Se genes are present, the secretor enzyme (FUT2) first converts the precursor substance into____ antigen. • The Lewis enzyme (FUT3) then acts on this H antigen to form____ antigen. • This means that Leb antigen is only formed in individuals who are both_____ and _____ positive

Answer 30

H Le^b Lewis-positive (Le) and Secretors (Se).

Question 31

Individuals with the lele Genotype (Lewis-negative) • If a person inherits two non-functional le alleles (lele), they cannot produce____ antigens. • These individuals have the ______phenotype and may be either ABH secretors or non-secretors.

Answer 31

Lewis Le(a–b–)

Question 32

Lele or LeLe, sese Phenotype???

Answer 32

Le(a+b-)

Question 33

Lele or LeLe, SeSe or Sese Phenotype???

Answer 33

Le(a-b+)

Question 34

lele, SeSe, Sese, or sese Phenotype???

Answer 34

Le(a-b-)

Question 35

LeLe or Lele, SeSe or Sese (Incomplete enzyme activity)

Answer 35

Le(a+b+) (Rare)

Question 36

individuals (Leb positive) are the most common phenotype in ***whites and blacks.***

Answer 36

Le(a–b+)

Question 37

individuals (Lewis-negative) are more common in ***blacks*** than in whites.

Answer 37

Le(a–b–)

Question 38

individuals are rare in whites and blacks but more common in Asians (10–40%).

Answer 38

Le(a+b+)

Question 39

Lewis Antigens Are Not Found on______ RBCs: • Cord blood RBCs lack Lewis antigens. • Lewis antigen expression is acquired during the first few years of life as the glycolipids accumulate in plasma. • Pregnancy reduces the expression of Lewis antigens, leading to weaker antigen expression on maternal RBCs.

Answer 39

Newborn

Question 40

Lewis Antigens Are Resistant to Enzymes: • Lewis antigens are not destroyed by common enzymes like (4) • Instead, enzyme treatment enhances Lewis antibody reactivity, leading to stronger agglutination or even hemolysis.

Answer 40

ficin papain dithiothreitol (DTT) glycine-acid EDTA.

Question 41

T or F Lewis antibodies are ***naturally occurring*** antibodies that are produced without prior exposure to red blood cells (RBCs).

Answer 41

TRUE

Question 42

Unlike other clinically significant blood group antibodies, Lewis antibodies are usually______, which means they do not cross the placenta and do not cause hemolytic disease of the fetus and newborn (HDFN).

Answer 42

IgM

Question 43

Lewis antibodies are produced by ____ individuals

Answer 43

Le(a-b-) individuals

Question 44

is the most commonly encountered Lewis antibody and is usually IgM. Naturally occurring and produced by Le(a–b–) individuals.

Answer 44

Anti-Le^a

Question 45

Lewis antibodies Reacts more in_____ than in blood groups _____ and ____ ○ Because _____ has more H antigen

Answer 45

group O than A or B Group O

Question 46

May activate complement and may cause in-vivo and in-vitro hemolysis

Answer 46

Lewis antibodies

Question 47

Occur frequently in pregnant women ○ diluted Le a and Le b ■ Due to plasma volume expansion

Answer 47

Lewis antibodies

Question 48

Most commonly encountered antibody

Answer 48

ANTI-Le^a

Question 49

→ produces Anti-Leª (antibody)

Answer 49

Le^b Antigen

Question 50

Not common and not as reactive Since the concentration of Le gene is smaller than Se (secretor) gene

Answer 50

ANTI-Le^b

Question 51

Formerly known as anti-Le^x

Answer 51

ANTI-Le^ab

Question 52

This antibody will only be formed, when the patient's blood type is null or Le(a-b-)

Answer 52

ANTI-Le^ab