BB .3 Ag-Ab Charac

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.

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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

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BB .3 Ag-Ab Charac