The Lewis System

Question 1

Which 3 genes does this system depend on?

Answer 1

H, Se and Le

Question 2

Where are their antigens made?

Answer 2

Primarily made from endothelial cells of bowel, secreted into fluids and absorbed onto the RBC membrane

Question 3

Lewis antigens present in plasma vs. secretions

Answer 3

Plasma = glycolipids
Secretions = glycoproteins

Question 4

What are the Lewis antibodies? Are they clinically significant?

Answer 4

• Anti-Lea, Anti-Leb
• IgM
• Not usually significant

Question 5

How does the development of these antigens work in newborns?

Answer 5

• Development begins in first week, continues up to 6 years

- Newborns usually have pheno Le(a-b-)

Question 6

How is Lewis similar to ABO?

Answer 6

• Produces a transferase

- Located on chromosome 19 (like Se + H)

Question 7

How is the Lewis group determined?

Answer 7

• Must have H substance to have Leb

- Always has a little bit of Lea (not usually detected when Leb is present.

Question 8

What happens in secretions when you have the amorph gene? (lele)

Answer 8

No Lewis gene will be secreted. Regardless of the Se gene

Question 9

What happens to the Lewis phenotype when the secretor gene is sese?

Answer 9

Can only make Lea pheno = Le(a+b-)

Question 10

What is the outcome if Bombay?

Answer 10

Lewis requires H to make Leb, so there won’t be any Leb

Question 11

Why can pregnant woman experience a change in Lewis?

Answer 11

Suppression of levels of transferase enzymes by steroid hormones that are produced.