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44 Cards in this Set

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What is the H antigen?
Precursor found on all human RBCs

This is the foundation upon which A and B Ags are made
What is added onto the H Ag to make it an A Ag?
N-acetyl-galactosamine

NOTE: this is added onto a D-galactose residue
What is added to the "precursor substance" to complete H Ag synthesis?
L-fucose
What is added onto the H Ag to make it a B Ag?
D-galactose

NOTE: this is added onto a D-galactose residue
What is H Ag synthesis controlled by?
A dominant gene, H
What phenotype (blood type) has the most H Ag?
Type O

This is because the O allele doesn't direct any modification of the H Ag
The majority of Native Americans are what blood type?
Type O
How are blood types distributed amongst blacks and orientals?
~50% Type O
~25% each of Type A and B
<5% of Type AB
How are blood types distibuted amongst whites?
~45% Type O
~40% Type A

~10% Type B
~5% Type AB
What Abs do humans produce by 6 months of age?
(w/ regards to blood types)
Abs against those antigens which they lack
By how old, do humans produce blood type Abs?
6 months of age
Blood type Abs in Type A and Type B people are of what class?
Predominantly IgM
Blood type Abs in Type O people are of what class?
Mixture of IgG and IgM
In incompatible tranfusions, what does the mortality rate depend on?
Amount of blood received

25% for over 500 ml
44% for over 1000 ml
What type of Abs are used in the blood bank to phenotype samples?
IgG
What is forward grouping?
Phenotype of the patient's RBCs

Determined by reacting anti-A and B Abs against patient CELLS
What is reverse grouping?
Testing pt serum for Abs

A and B RBCs are reacted against patient's SERUM
What is the D Ag?
Epitope that qualified people as being Rh+
How is the D Ag inherited?
Autosomal dominant
What % of people are D positive?
~85%
When are Abs against D formed?
Only upon exposure

NOTE: this is different than other blood type Abs
(Remember, others are formed naturally by 6 months of age)
How are blood samples D Ag typed?
Using forward grouping
What is the Antibody screen?
Test to detect common Abs in patient's SERUM

Type O cells w/ the common Ags are reacted w/ patient's SERUM
Anti-human globulin is added

If Abs are present in pt. serum, agglutination will occur
What is the Crossmatch?
Identical to the Ab screen, except that cells are from unit being transfused
In what circumstance can whole blood be transfused?
ONLY if donor and recipient are identical ABO type
Why can you not transfuse type O whole blood into an A or B recipient?
(large volume transfer)
Evenutally, anti-A or anti-B Abs in Type O plasma will react

NOTE: a SMALL quantity of incompatible plasma is not harmful
What type is the universal recipient?
AB
What type is the universal donor?
O
How many D positive transfusions can a D negative person receive?
One, before they develop Abs
Who can Type O be transferred to?
Only to Type O pts.
Who can Type AB plasma be transferred to?
To anyone
Are there type restrictions on platelet transfusions?
NO

NOTE: a D neg pt. CAN be immunized by a platelet tranfusion
(due to the few red cells present in platelet concentrate)
Abs are usually formed to which Ags on platelets?
HLA Ags
What is leukocyte reduction?
Filtering to remove 3 to 4 logs of WBCs

Reduces alloimmunization to HLA Ags in platelet transfusions

Works ~90% of time
What are the 3 indications for use of leukocyte reduced products?
Prevent febrile, non-hemolytic transfusion rxns.
Prevent transmission of CMV
Prevent alloimmunization to platelets
What is a febrile NON-hemolytic transufsion reaction (FNHTR)?
Temp elevation of one degree C or more within 2 hrs of transfusion

Fever is caused by cytokines from leukocytes and HLA Abs
How are FNHTRs treated?
Acetaminophen and observation
What is urticaria?
Hives

In blood bank, due to type I hypersensitivity to transfused unit
Acute INTRAvascular hemolytic transfusion reaction

What is it almost always due to?
ABO incompatibility

NOTE: this is VERY serious

Can cause hypotension --> renal failure, DIC
What type of Abs are involved in ACUTE INTRAvascular HTR?
IgM
What type of Abs are involved in DELAYED EXTRAvascular HTR?
IgG
What is Delayed EXTRAvascular HTR caused by?
Abs OTHER THAN ABO

These were at too low a titer to be detected by the Ab screen

An anamnestic response is elicited
In Delayed EXTRAvascular HTR, what are transfused RBCs removed by?
Splenic macrophages

Occasionally, complement will be activated (this is more severe)
In Acute INTRAvascular HTR, what are transfused RBCs removed by?
Complement