Lecture 3 Flashcards
Where are lewis antigens made?
manufactured by tissue cells and secreted into body fluids
not manufactured by the red blood cell.
antigen production for Lewis antigens depend on what?
Lewis genes and a secretor gene
(Le)
Lewis genes
What chromosome is the Lewis gene located on?
Chromosome 19
What does this Le code for
glycosyltransferase, α-4-L-fucosyltransferase
The Lewis (a+b-) Phenotype
Lea substance is secreted regardless of the secretor status
An individual can be a nonsecretor (sese) of ABH and still secrete Lea
The Lewis (a+b-): Secretion
Lewis enzyme has been detected in saliva, milk, sub-maxillary glands, gastric mucosa, and kidney and cyst fluids
The Lewis (a-b+) Phenotype
Secretors, the result of the genetic interaction of Lele and Sese genes
is absorbed onto the RBC from plasma
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+)
The Lewis (a-b-) Phenotype
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
What do the point mutation of The Lewis (a-b-) Phenotype lead to?
give rise to a non-functional or partially active Lewis transferase (Lew) causing the negative expression of the Lewis antigen on RBC’s
lele genotype is much more common in which group?
blacks
Le(a-b-) nonsecretors express as what?
type 1 precursors
What is the most common Le phenotype
Le (a+b-)
Lewis antigens or substances found in the secretions are?
glycoproteins, as are the ABH substances from secretors
In plasma Lewis antigens are?
glycolipids (glycosphinglolipids)
Antigens are carried by ?
lipoproteins present in plasma that adhere to RBC membranes, form glycosylceramides
Cord cells and RBCs from newborn infants phenotype as what?
Le(a-b-).
infants do secrete what?
Lea substance in their saliva
In individuals who inherit Le and Se genes, a transformation can be followed from what?
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
individuals who inherit Le and sese genes phenotype as
Le(a-b-) at birth
Le(a+b-) after 10 days
Le(a+b-) phenotype persists throughout life
Individuals with lele genes phenotype as?
Le(a-b-) at birth and for the rest of their lives
A decrease in expression of Lewis antigens has been demonstrated on what?
RBCs from many pregnant women, resulting in Le(a-b-) phenotypes during gestation
Lack of expression of Lewis antigens has been demonstrated on the RBCs of patients with what?
cancer, alcoholic cirrhosis, and viral and parasitic infections
transformation of Lewis-positive phenotypes to Lewis-negative phenotypes is caused by?
abnormal lipid metabolism, changes in triglycerides and high density lipoproteins and/or other neoplastic changes occurring in cancer patients
Lewis antibodies are considered naturally occurring because?
they are present without previous exposure to the antigen-positive RBC’s
Lewis Antibodies are considered
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
Hemolysins
An antibody that activates complement, leading to cell lysis
Lewis antibodies occur quite frequently
in the sera of pregnant women
Anti-Lea and anti-Leb may occur together and can be neutralized by?
the Lewis substance present in plasma or saliva
Anti-Lea
the most commonly encounter antibody
often of the IgM class; however, some may have IgG
Anti-Lea: IgG form
does not bind to the RBCs as efficiently as does the IgM, not generally detected in routine blood bank procedures
do not make anti-lea?
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
Anti-Leb
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-)
