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Immunohematology > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Where are lewis antigens made?

A

manufactured by tissue cells and secreted into body fluids
not manufactured by the red blood cell.

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2
Q

antigen production for Lewis antigens depend on what?

A

Lewis genes and a secretor gene

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3
Q

(Le)

A

Lewis genes

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4
Q

What chromosome is the Lewis gene located on?

A

Chromosome 19

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5
Q

What does this Le code for

A

glycosyltransferase, α-4-L-fucosyltransferase

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6
Q

The Lewis (a+b-) Phenotype

A

Lea substance is secreted regardless of the secretor status
An individual can be a nonsecretor (sese) of ABH and still secrete Lea

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7
Q

The Lewis (a+b-): Secretion

A

Lewis enzyme has been detected in saliva, milk, sub-maxillary glands, gastric mucosa, and kidney and cyst fluids

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8
Q

The Lewis (a-b+) Phenotype

A

Secretors, the result of the genetic interaction of Lele and Sese genes

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9
Q

is absorbed onto the RBC from plasma

A

Only Leb
probably due to a higher concentration of Leb in plasma allowing Leb-soluble antigen to compete more successfully for sites of adsorption
RBCs of these individuals always phenotype as Le(a-b+)

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10
Q

The Lewis (a-b-) Phenotype

A

Secretors or Nonsecretors
Lack the Lewis antigens on the RBCs of this group is caused by rather the specific point mutation in the Le gene

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11
Q

What do the point mutation of The Lewis (a-b-) Phenotype lead to?

A

give rise to a non-functional or partially active Lewis transferase (Lew) causing the negative expression of the Lewis antigen on RBC’s

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12
Q

lele genotype is much more common in which group?

A

blacks

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13
Q

Le(a-b-) nonsecretors express as what?

A

type 1 precursors

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14
Q

What is the most common Le phenotype

A

Le (a+b-)

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15
Q

Lewis antigens or substances found in the secretions are?

A

glycoproteins, as are the ABH substances from secretors

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16
Q

In plasma Lewis antigens are?

A

glycolipids (glycosphinglolipids)

17
Q

Antigens are carried by ?

A

lipoproteins present in plasma that adhere to RBC membranes, form glycosylceramides

18
Q

Cord cells and RBCs from newborn infants phenotype as what?

A

Le(a-b-).

19
Q

infants do secrete what?

A

Lea substance in their saliva

20
Q

In individuals who inherit Le and Se genes, a transformation can be followed from what?

A

Le(a-b-) phenotype at birth
Le(a+b-) after 10 days
Le(a+b+)
finally to Le(a-b+), the true Lewis phenotype after 6 to 7 years

21
Q

individuals who inherit Le and sese genes phenotype as

A

Le(a-b-) at birth
Le(a+b-) after 10 days
Le(a+b-) phenotype persists throughout life

22
Q

Individuals with lele genes phenotype as?

A

Le(a-b-) at birth and for the rest of their lives

23
Q

A decrease in expression of Lewis antigens has been demonstrated on what?

A

RBCs from many pregnant women, resulting in Le(a-b-) phenotypes during gestation

24
Q

Lack of expression of Lewis antigens has been demonstrated on the RBCs of patients with what?

A

cancer, alcoholic cirrhosis, and viral and parasitic infections

25
Q

transformation of Lewis-positive phenotypes to Lewis-negative phenotypes is caused by?

A

abnormal lipid metabolism, changes in triglycerides and high density lipoproteins and/or other neoplastic changes occurring in cancer patients

26
Q

Lewis antibodies are considered naturally occurring because?

A

they are present without previous exposure to the antigen-positive RBC’s

27
Q

Lewis Antibodies are considered

A

immunoglobulin M (IgM) in nature
because they are IgM, these hemolysins can activate complement and therefore can occasionally cause in vivo and in vitro hemolysis

28
Q

Hemolysins

A

An antibody that activates complement, leading to cell lysis

29
Q

Lewis antibodies occur quite frequently

A

in the sera of pregnant women

30
Q

Anti-Lea and anti-Leb may occur together and can be neutralized by?

A

the Lewis substance present in plasma or saliva

31
Q

Anti-Lea

A

the most commonly encounter antibody
often of the IgM class; however, some may have IgG

32
Q

Anti-Lea: IgG form

A

does not bind to the RBCs as efficiently as does the IgM, not generally detected in routine blood bank procedures

33
Q

do not make anti-lea?

A

Persons who are Le(a-b+)
the Lea antigen structure is contained within Leb antigen epitope and Le(a-b+) persons have Lea substance present in their plasma and saliva

34
Q

Anti-Leb

A

not as common or generally as strong as anti-Lea
usually an IgM agglutinin, it does not fix complement as readily as anti-Lea
produced by an Le(a-b-)

Immunohematology (16 decks)

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