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7/31/2019 BB .3 Ag-Ab Charac
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ANTIGEN ,
ANTIBODY
CHARACTERISTICS
&
REACTIONS
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Characteristics of an Antigen
> Must be foreign to the body
> Must possess a high molecular weight
> Must gain entry to the animal body
> Must possess high order of specificity
> Must possess chemical complexity
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Characteristics of an Antibody
> Specificity
> Heterogeneity
> Recognition to oneself
> Memory
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1. Complete and Incomplete Antibodies
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Immunoglobulins Involved in Immunohematologic reactions
IgG disulfide bond; 14nm
IgM pentameric / pentamer, first line of defense because they are th
first one to be produced because of its antigenic structure; 35 nm
**IgA monomeric lines with mucosal surface and predominantly is i
with secretion
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Characteristics of IgG and IgM
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Varying Lattice fromation
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2. Effect of Surface charge
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3. Pretreatment of Red Cells
> to reduce the Zeta Potential
- Protamine ( hexadimethrine bromide)- Polystyrene
4. Use of Protein Media
> To reduce the zeta potential
Enzyme : bromelin . 0.5% , pH 5.5ficin & trypsin 0.1% , pH 7.3Papain ..0.1% , phH 6.5
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5. Use of Antihuman Globulin
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6. Chemical Reduction of IgG
7. Effect of pH
8. Effect of Temperature
4 degrees to < 37 degrees (cold reacting Ab) 37 degrees centigrade (warm reacting Ab)
Note: Abs detected at 37 degrees Centigradeare significant
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9. Effect of Ionic Strength
Short incubation period needed LISS (0.2% NacL and 0.7% Glucose)
10. Effect of Cell Dosage
Heterozygous productionAO ---- A antigen
AB ---- A , and B antigensBO ---- B antigen
Homozygous productionAA ----- A antigenBB ----- B antigen
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11. Effect on the Location of the Antigen
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Considerations when reading AgglutinationReactions
> All patients must be O
> False negative
Occurs before additionof reagents (Ag or Ab)
How to check?
Centrifuge the mixture, if none settled : Positive
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Causes of Hemolysis
> Excessive pulling of plunger during blood collection
> Using hypotonic solution during red cell preparation
Red CellSuspension
2% 5 %
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2. Rouleaux Formation
> Stack of coin
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Falsely Interpreted Reactions
1. Sample Problems
> Plasma / Serum
Serum contain fibrin strands :
not completely coagulated
Elevated amounts of Proteins andPresence of abnormal Proteins
> Red Cells
coated in-vivo :IAHA, TR, HDN
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Importance of Mixing
Insufficient or delayedmixing of serum tubesmayresult in delayed
clotting.
Inadequate mixing ofanticoagulant tubes may
result inplatelet clumping,clotting or incorrect testresults.
http://us.gbo.com/preanalytics/admin/modules/document_repository/docs/b0a06bd67
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2. Reagents Used
> Degraded potency
Improper storage
Proper storage : 2 8 degrees Centigrade
> Antisera contain other antibodies
> Concentration of Saline Solution
Proper concentration : 0.85% to 0.90%
Hypotonic or Hypertonic
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3. Equipment Problems
> Incorrect calibration of centrifuge machine
> Contaminated glassware used
4. Technical Errors
> Commonly done by MedTechs
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CAUSES OF FALSE POSITIVE REACTIONS IN AGGLUTINATION
Causes RemedyOver centrifugation Regulate speed and time
Contaminated glassware Keep supplies covered and stored in aclean place
Autoagglutination Use control and Saline
Cross reactivity Use purified reagents and monoclonal Ab
Presence of Heterophil Abs Use pre absorbed serum and
Delayed reading slide test Read results immediately
Too heavy Red cell suspension Prepare Red Cell Suspension properly
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CAUSES OF FALSE NEGATIVE REACTIONS IN AGGLUTINATION
Causes RemedyUnder centrifugation Regulate speed and time
Inadequate red cell washing Wash red cells properly
Reagents not active Proper storage of reagents
Delays in carrying out the
procedure
Once a procedure is begun, follow
through until the end withoutdelay
Insufficient incubation time andtemperature
Observe proper time and temperature
Too light red cell suapension Prepare red cell suspension properly
Failure to add AHG Monitor the addition of reagents
Prozone phenomena Dilute the serum properly and repeat thetest
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Teach us to number our days aright that we may gain wisdom.Psalm 90:12