Types of Agglutination in Immunology

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Questions and Answers

What is the significance of the β-subunit in hCG?

It is present in all hormones related to pregnancy.

It is unique to hCG and increases specificity. (correct)

It decreases the sensitivity of pregnancy tests.

It is identical to α-subunit in function.

Why is the first morning urine specimen preferred for pregnancy testing?

It is the easiest specimen to collect.

It provides a larger volume for testing.

It has the highest concentration of hCG. (correct)

It is less likely to contain contaminants.

What is a potential reason for a false-negative result in pregnancy tests?

Excessive hydration before testing.

The sample being taken before detectable hCG levels are reached. (correct)

Testing at a high level of hCG.

The use of a non-monoclonal antibody.

Which factor is NOT critical for the quality of test results?

The age of the test kit components. Signup and view all the answers

What might cause a false-positive result in a pregnancy test?

Recent hCG injection to trigger ovulation. Signup and view all the answers

Which factor has the greatest impact on the strength of Ag-Ab interactions?

Zeta potential Signup and view all the answers

Why does low ionic strength saline (LIS) enhance Ag-Ab reactions?

It decreases ionic strength of the environment. Signup and view all the answers

Which antibody is considered to be more efficient at agglutination?

IgM Signup and view all the answers

What is the primary reason for the shielding effect in zeta potential?

Presence of Na+ and Cl− ions. Signup and view all the answers

What impact does reducing the ionic strength of a solution have on Ag-Ab interactions?

Allows for enhanced agglutination. Signup and view all the answers

How many antigenic determinants does a typical RBC blood group antigen have?

1.5 million Signup and view all the answers

Which factor does NOT influence Ag-Ab association?

Blood type Signup and view all the answers

What is the effect of the Ag-Ab ratio on agglutination reactions?

Both low and high ratios can affect results. Signup and view all the answers

What type of particles can be used in passive agglutination?

Insoluble particles like latex or RBCs Signup and view all the answers

Which of the following is a characteristic of reverse passive agglutination?

Visible aggregates can form with specific antibodies Signup and view all the answers

What indicates a positive result in the agglutination test?

Red blood cells diffuse Signup and view all the answers

What could lead to false positive results in liposome-enhanced testing?

Nonspecific aggregation of lipids Signup and view all the answers

Which type of assay can be enhanced by using Secondary Ab Anti human globulin (AHG)?

Agglutination test Signup and view all the answers

Which antigen is typically not tested using latex particle agglutination?

Human Chorionic Gonadotropin (HCG) Signup and view all the answers

Which of the following is NOT a precipitation reaction type covered in the lab?

Enzyme-linked immunosorbent assay Signup and view all the answers

What is a key feature of co-agglutination testing?

Enhances visibility without enhancing specificity Signup and view all the answers

Which factor is critical in the sensitization phase of agglutination?

Chemical reaction between Antigen and Antibody Signup and view all the answers

What is the expected result when HBsAg from the patient reacts with Anti-HBsAg sensitized RBC in HA inhibition?

Inhibition of agglutination Signup and view all the answers

How long after the last menstrual period do peak levels of HCG typically occur?

2 to 3 months Signup and view all the answers

What results in negative results during the haemagglutination inhibition test?

Influenza virus presence Signup and view all the answers

Which of the following is a characteristic of passive agglutination?

It involves insoluble particles bound to any antigen. Signup and view all the answers

What is the role of membranes in the context of RBC agglutination tests?

They may be involved in membrane attack complexes Signup and view all the answers

What is one potential drawback of using liposome-based enhancement in agglutination testing?

They tend to aggregate nonspecifically. Signup and view all the answers

Which method is typically discussed in the lab related to positive results in serological tests?

Flocculation test Signup and view all the answers

What is the optimal pH range for antigen-antibody reactions?

6.5 to 7.5 Signup and view all the answers

What are the temperature ranges for cold and warm reacting antibodies IgM and IgG respectively?

4°-22° C for IgM; 37° C for IgG Signup and view all the answers

What could cause antigenic hindrance during antibody binding?

Adding excessive amounts of antibodies Signup and view all the answers

Which method is NOT used to enhance agglutination?

Increasing temperature to 100°C Signup and view all the answers

What characterizes lattice formation in antibody-antigen reactions?

Influence by zeta potential Signup and view all the answers

What is a pseudoagglutination reaction?

False clumping of particles without true aggregation Signup and view all the answers

Which term describes assays that involve antibody-antigen reactions?

Immunoassays Signup and view all the answers

Which component is crucial for the immediate reading in microplate agglutination reactions?

Centrifugation Signup and view all the answers

Study Notes

Agglutination Types

Passive Agglutination: Involves insoluble particles attached to any antigen (viral, CRP, hormones, drugs).
Common insoluble particles: latex, colloidal substances, charcoal, gelatin, resin beads, and RBCs.
Reverse Passive Agglutination: Insoluble particles are coated with antibodies for detection.
Coatable particles include colloidal latex, charcoals, gelatin, resin beads, and RBCs.
Co-agglutination and Liposome-Enhanced Testing: Variations involving antigens bound to particles like liposomes, which increase visibility but can cause false results due to non-specific aggregation.

Immunologic Assays with Latex Particles

Tests performed via latex particle agglutination include:
- C-reactive protein
- Immunoglobulin G rheumatoid factors
- Immunoglobulin M rheumatoid factors
- Rubella antibodies (currently using ELISA).

Human Chorionic Gonadotropin (hCG)

A glycoprotein hormone secreted by the trophoblast of the developing embryo.
Peak levels occur 2 to 3 months after the last menstrual period (LMP).
Composed of two subunits: α (common in various hormones) and β (unique to hCG).
Rapidly increases in urine or serum during early pregnancy.
Use of monoclonal antibodies targeting the β-subunit enhances specificity.

Pregnancy Testing Protocols

Principle: Latex particles coated with anti-hCG antibodies detect hCG in urine.
Specimen Requirements:
- First morning urine for highest hormone concentration.
- Specific gravity should be at least 1.018.
- Samples can be refrigerated for up to 2 days or frozen at -20°C for at least 1 year.
Positive Results:
- Technical errors can affect results; reagents should not be expired.
- Latex reagent must be well shaken, and agglutination readings should be made within 3 minutes.

False Results

False-Negative: Can occur if testing is done before detectable hCG levels or with low urine concentration; serum samples may be needed.
False-Positive: Can arise from using monoclonal antibodies against α units or after hCG injections for ovulation.

Factors Affecting Test Quality

Incubation time with the antibody source and the quality and amount of the antibody conjugated to the carrier significantly influence results.
Secondary antibodies can enhance agglutination.

Mechanisms of Agglutination

Agglutination involves sensitization (Ag-Ab reaction) followed by lattice formation (aggregation through cross-linking).
Factors influencing sensitization include particle charge, antibody type, Ag-Ab ratio, antigenic determinants, pH, and temperature.

Methods to Enhance Agglutination

Techniques include using low ionic strength saline, proteolytic enzymes, colloids, and antihuman globulin.

Graded Agglutination Reactions

Pseudoagglutination: False appearance of clumping may occur when particles aggregate nonspecifically.

Microplate Agglutination Reactions

Allows testing of large samples on a single plate, optimizing time and efficiency by bypassing labeling test tubes.
Typically uses U-shaped microplates in immunohematology, which are centrifuged for immediate reading.

Summary on Immunoassays

Immunoassays involve antibody-antigen interactions.
Precipitation Reactions: Soluble antigens and antibodies form insoluble products, with various techniques such as double gel diffusion, radial immunodiffusion, and more for detection.

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Description

This quiz covers various types of agglutination, focusing on passive and reverse passive agglutination. Participants will learn about the role of different particles and antibodies in these processes. Test your knowledge on how these agglutination methods are applied in immunological contexts.