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55 Cards in this Set

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  • Back
What is an antigen?
a substance that, when introduced into the body of an immuno-competent host, will cause the production of a specific antibody
What are Antibodies?
part of a persons immunie response to a specific stimulus (antigen)
What is Agglutination?
-Visible results of an antibody-antigen response (usually refers to red cells)
-used too see if rxn took place
What is a naturally occuring antibody?
an antibody response WITHOUT a known stimulus
What is an immune induced antibody?
an antibody response to a known stimular
Name 2 RBC antigen systems
ABO and Rh (there are many more)
Name some related blood group antigens (related in lewis system)?
ABO, H, P, I, Lewis Systems

are related blood group antigens
Where do ABO, H, P, I Lewis systems reside?
on carbohydrate molecules attached to the RBC
What do ABO, H, P, I, Lewis systems reflect?
they reflect the activity of genetically determined glycotransferase enzymes
Antigens appear when ...
transferase enzymes add individual sugars to sites on short chains of sugars called oligosaccharides
In antigens, the H gene causes the production of...
an enzyme that adds fucose (a sugar) to a basic chain
Enzymes that add the sugars to form A and B antigens can only add the sugars under what circumstances?
they can only add the sugars if a fucose is already attached

So you must ahve the H gene before you can add A or B antigen
A gene causes the attachment of...
B gene causes the attachment of...
Genes for AB cause the attachemnt of...
both n-acetylgalactosamine and galactose
Genes for O (amorph) cause the attachment of...
If there is no H gene, what type of pheno types is that?
bombay phenotype
Who discovered ABO blood groups?
Karl Landsteiner in 1900 (types A, B, O)

AB group was discovered by his students in 1902
What are glycosphingolipids?
They carry A and B oligosaccharides and are integral parts of the membrance of the red cells, epithelial cells, and endothelial cells
-present in soluble form in plasma
What may be carried by secreted body fluids such as saliva, semen, and breast milk?
identical oligosaccharides (if the person carries the Se gene)
WHat type of antibodies do people express?
-people poseess antibodies directed against the A or B antigen lacking on their own red blood cells
(poseess antibodies for what ever thet don't have)

-antibodies are naturally occuring and mainly IgM

-antibodies react at room temp and fix complement readily
It is theorized that antobody response is in response to....
bacterial stimuli
what types of antibodies do newborns have?
Newborns possess A and B antigens but lack antibodies of their own against A or B antigens
(so technically, you could give a newborn anything because they don't have any antibodies)
What is Forward Grouping?
-tests that use anti-A and anti-B and anti-AB to determine the presence or absence of antigens
-known reagens (antibodies) are mixed with unknown cells and allowed to react. if the antibody attached to the cells, you know the antigen is present (we see agglutination)
-often described as direct or RBC tests
What is Reverse Grouping?
-use of known reagent A cells and B cells with unknown serum allows us to determine the blood type based on the serum rxn (since you produced antibodies only against the antigens that your RBC lack)
People with A RBCs produce....
anti B in their serum
People with B RBCs produce....
anti A in their serum
People with AB RBCs produce ...
no antibodies for A or B
People with O RBC's produce....
both anti-A and anti-B in their serum
Who was the Rh system discovered by?
Levine and Stetson in 1939

Anti-D serum was found in the serum of a woman whose fetus had hemlytic disease of the newborn and who experienced a hemolytic transfusion reaction when transfused with her husbands blood (mom is exposed to anti D blood from the fetus at some point d/t a previous pregnancy and develops antibodies against D. Then when exposed against - her body destroys it)
What five antigens does the Rh system include?
D, C, E, c, e, and amorph d
HOw common is the d antigen?
85% of human RBCs
Typing for the D antigen:
-d antigen has greater antigenicity than any of the other RBC antigens
-80% of d-negative persons stimulated with D positive blood will respond with the production of D antigen
-bc of its antigenicity and its importance in pregnancy, it is includes in routine typing studies and all donor units are allowed to react with unknown red cells to determine the types of those cells.
-generally NOT IgM, therefore rxns must be enhance with heat, albumin, or specifically modified reagents or reaction systems
What is a direct antoglobulin test?
-useds antihuman globulin (an antibody that reacts with human globulins) to test for in vivo antibody attachment to the RBC
-used to detect in-vivo coating of RBCs by antibody or complement
-washed RBCs from a patient or donor are mixed with anto-human globulin reagents and observed for agglutination
-antiserum can be broad spectrum (detects all classes of antibody as well as complement or specific for a single antibody class or complement)
What is the normal antiglobulin test result?
-normally negative (no antibody coating the RBC)
What are some situations where it may be useful?
-testing for hemolytic disease of the newborn
-testing for transfusion rxns
-testing for warm or cold AIHA (autoimmune hemolytic anemia)
Which tube should be used for a direct antiglobulin test?
EDTA anticoagulant (lavendar tube)

-EDTA chelates calcium. Calcium is the necessary for the binding of complement to red cells
-EDTA ensures that any complement bound to the cells was bound prior to collectio of the sample
Which blood can you use in the direct antiglobulin test?
-cells from clotted blood (red tube)

NOT cells from serum separator tube
What are possible causes of positive direct antiglobulin test?
-alloantibodies reacting with transfused cells
-alloantibodies in maternal serum that cross the placenta and coat infant cells
-antibodies directed against certain drugs that attach to RBC membrane (eg pennicllin)
Indirect antiglobulin test
-uses known cells to detect the presence of antibodies in the serum of a patient
-pt serum is allowed to react with known cells in a series of conditions in an effort to allow antibodies (if present) to bind to the cells
-uses albumin or low-ionic strength solutions, enzymes, and anti-human globulin
What is a normal indirect antiglobulin test result?
What are some possible uses for indirect antiglobulin test?
-part of a type and screen or type and cross match procedure
-to screen OBs to alert a provider of the possibility of hemolytic disease of the newborn
-part of an auto-immune hemolytic anemia work up
What is a type and cross used for?
USed to ensure that donor cells are compatible with the recipients serum
How does the type and cross work?
Recipient blood is grouped and typed and an indirect antiglobulin test is performed to look for unexpected antibodies in the serum that could result in a transfusion reaction
Then donor cells are allowed to react with the recipients serum in a series of conditions
What do technicians look for in a type and cross?
agglutination or hemloysis in various phases of the test
What is the goal of type and cross?
to ensure that the product will no harm the patient and that it will be therapeutic
In a type and cross, what is matched and what is not?
RBC are cross matched

plamsa, platelets, and cryoprecipitate are not cross matched
What percent of transfusion accidents are from administrative error rather than technical failure?
What are causes of administrative error in transfusions?
-samples collected on the wrong patient
-sample not appropriately labeled
-units of blood being given to the wrong patient
-units of blood being inappropriately transfused (transfusion exceeding 4 hours or mixed with D5W or inappropriate product)
How long does a cross match take to complete?
about 1 hour
What are alternatives to a full crossmatch?
-group and type specific blood
-o negative PRBCs
What are all donor units tested for?
-ABO and Rh
-Unexpected antibodies to red cell antigens
-serologic tests for syphilis
-EIA tests for viral antigens (HBsAg, HIV antigen)
-EIA tests for antibodies (HIV 1 and 2, anti-HBc, Anti-HCV, Anti-HTLV)
When should tranfusion take place?
only when the anticipated benefits outweight the risks
What are blood products for transfusion?
-whole blood
-RBC (most commonly used)
-granulocytes (single donor or pheresis)
-fresh frozen plasma (frozen within 4 hrs so it has 100% clotting factors)
-cyroprecipitate (concentrated factor 8 often used in hemophiliacs)
-frozen red cells (no plasma, so you dont have to worry about a or b antibodies, very expensive)
What are pharmacologic alternatives to transfusion?
-blood cell growth factors
-DDAVP (causes the release of HMW-vWF - used to treat platelet fcn disorders)
-vitamin k
-fibrinolytic inhibitors