Immunoelectrophoresis MCQs With Answer

Immunoelectrophoresis MCQs With Answer is a concise, targeted quiz series created for M.Pharm students specializing in immunotechnology. This set focuses on immunoelectrophoretic techniques — their principles, variants, practical parameters, interpretation of precipitation patterns, strengths and limitations, and applications in clinical and research settings. The questions emphasize deeper conceptual understanding: gel choice, buffer pH, electrophoretic mobility, precipitin patterns (identity, partial identity, spur), quantitative formats like rocket electrophoresis, and modern alternatives such as immunofixation. Each MCQ is designed to reinforce laboratory decision-making and data interpretation skills relevant to protein characterization, monoclonal gammopathies, and assay optimization in advanced pharmaceutical and immunological contexts.

Q1. What is the primary principle underlying classical immunoelectrophoresis?

• Direct antigen-antibody agglutination in liquid phase
• Separation by electrophoresis followed by immunodiffusion to form precipitin arcs
• Chromatographic separation on paper with enzyme-linked antibodies
• Antibody immobilization on nitrocellulose followed by western blot detection

Correct Answer: Separation by electrophoresis followed by immunodiffusion to form precipitin arcs

Q2. Which gel medium is most commonly preferred for immunoelectrophoresis due to low electroendosmosis and clear background?

• Agar
• Agarose
• Polyacrylamide
• Cellulose acetate

Correct Answer: Agarose

Q3. In an immunoelectrophoresis run, antigen mobility is primarily determined by which factor?

• Molecular weight only
• Temperature of electrophoresis
• pH of buffer relative to the antigen’s isoelectric point (pI)
• Concentration of agarose gel

Correct Answer: pH of buffer relative to the antigen’s isoelectric point (pI)

Q4. Which technique accelerates antigen-antibody precipitation by applying an electric field to drive reactants toward each other?

• Ouchterlony double diffusion
• Counterimmunoelectrophoresis
• Rocket electrophoresis
• Isoelectric focusing

Correct Answer: Counterimmunoelectrophoresis

Q5. Ouchterlony double diffusion is best described as which of the following?

• Single-dimension electrophoretic separation followed by antibody diffusion
• Double immunodiffusion in agar where both antigen and antibody diffuse toward each other
• Antibody immobilization on membranes with subsequent antigen overlay
• Two-dimensional isoelectric focusing followed by SDS-PAGE

Correct Answer: Double immunodiffusion in agar where both antigen and antibody diffuse toward each other

Q6. In an Ouchterlony plate, the appearance of a spur at the intersection of precipitin lines indicates which relationship between the antigens?

• Full identity (antigens are identical)
• Partial identity (antigens share some but not all epitopes)
• Nonidentity (antigens are completely different)
• Antigen degradation

Correct Answer: Partial identity (antigens share some but not all epitopes)

Q7. Which variant of immunoelectrophoresis is specifically designed for quantitation by producing a rocket-shaped precipitin peak proportional to antigen concentration?

• Crossed immunoelectrophoresis
• Immunofixation electrophoresis
• Laurell rocket electrophoresis
• Ouchterlony double diffusion

Correct Answer: Laurell rocket electrophoresis

Q8. Which statement best describes the prozone phenomenon in precipitation assays like immunoelectrophoresis?

• Excess antigen relative to antibody causes large visible precipitin lines
• Excess antibody relative to antigen prevents lattice formation and inhibits precipitation
• Low ionic strength enhances precipitation
• Precipitin arcs become sharper with increasing antibody concentration

Correct Answer: Excess antibody relative to antigen prevents lattice formation and inhibits precipitation

Q9. Compared to classical immunoelectrophoresis, which method provides higher sensitivity and specificity for detecting and identifying monoclonal immunoglobulins?

• Ouchterlony double diffusion
• Counterimmunoelectrophoresis
• Immunofixation electrophoresis (IFE)
• Plain agarose gel electrophoresis without immunoreaction

Correct Answer: Immunofixation electrophoresis (IFE)

Q10. Which factor most strongly affects the shape and position of precipitin arcs in a classical immunoelectrophoresis assay?

• Rate of antibody production in vivo
• Relative electrophoretic mobilities of antigen and antibody
• Temperature of gel staining only
• Molecular weight markers loaded in gel

Correct Answer: Relative electrophoretic mobilities of antigen and antibody

Q11. Which staining method is commonly used to visualize protein precipitin arcs on agarose gels after immunoelectrophoresis?

• Silver nitrate staining
• Coomassie Brilliant Blue
• Hematoxylin and eosin
• Gram staining

Correct Answer: Coomassie Brilliant Blue

Q12. Which pattern on an Ouchterlony plate indicates full antigenic identity between two samples?

• Two lines crossing with a spur
• Formation of a continuous smooth line of precipitation between wells
• No line of precipitation
• Multiple fragmented arcs with gaps

Correct Answer: Formation of a continuous smooth line of precipitation between wells

Q13. Electroendosmosis in agarose gels during electrophoresis refers to which phenomenon?

• Rapid heating of the gel causing protein denaturation
• Bulk flow of solvent through the gel matrix caused by fixed charges on gel fibers
• Migration of only negatively charged proteins toward the anode
• Formation of gas bubbles that disrupt mobility

Correct Answer: Bulk flow of solvent through the gel matrix caused by fixed charges on gel fibers

Q14. Crossed immunoelectrophoresis differs from classical immunoelectrophoresis primarily because it:

• Performs a second electrophoresis of antibody into antigen-containing gel allowing better quantitation and resolution
• Relies solely on diffusion without any applied electric field
• Uses nitrocellulose membranes instead of agarose
• Is exclusively qualitative and cannot be used for quantitation

Correct Answer: Performs a second electrophoresis of antibody into antigen-containing gel allowing better quantitation and resolution

Q15. Which of the following is a major limitation of classical immunoelectrophoresis in modern clinical laboratories?

• Excessive sensitivity leading to false positives
• Low sensitivity and time-consuming interpretation compared with newer methods
• Inability to separate proteins by charge
• Requirement for radioactively labeled reagents

Correct Answer: Low sensitivity and time-consuming interpretation compared with newer methods

Q16. In rocket electrophoresis, what measurement correlates directly with antigen concentration?

• Width of the precipitin base only
• Height (or length) of the rocket-shaped precipitin peak
• Color intensity after staining regardless of shape
• Number of precipitin peaks formed

Correct Answer: Height (or length) of the rocket-shaped precipitin peak

Q17. What is the commonly used buffer pH for serum protein separation in agarose immunoelectrophoresis?

• pH 5.0
• pH 7.0
• pH 8.6
• pH 10.5

Correct Answer: pH 8.6

Q18. Which assay adaptation is particularly useful when you need to identify the isotype (e.g., IgG, IgA, IgM) of a monoclonal protein?

• Ouchterlony double diffusion with nonspecific antiserum
• Immunofixation electrophoresis using specific anti-isotype antisera
• Plain agarose electrophoresis without immunoreagents
• Silver staining of polyacrylamide gels

Correct Answer: Immunofixation electrophoresis using specific anti-isotype antisera

Q19. Which of the following best describes the analytical sensitivity order for common diffusion/electrophoretic immunoassays (from highest to lowest sensitivity)?

• Ouchterlony > Immunoelectrophoresis > Immunofixation
• Immunofixation > Immunoelectrophoresis > Ouchterlony
• Immunoelectrophoresis > Immunofixation > Rocket electrophoresis
• All have identical sensitivity

Correct Answer: Immunofixation > Immunoelectrophoresis > Ouchterlony

Q20. When interpreting precipitin arcs, which observation most strongly suggests the presence of a monoclonal immunoglobulin in serum?

• Diffuse, broad polyclonal smear across multiple regions
• Single sharp, discrete arc or band corresponding to one immunoglobulin species
• Complete absence of any precipitation with polyvalent antisera
• Multiple overlapping faint arcs with no dominant band

Correct Answer: Single sharp, discrete arc or band corresponding to one immunoglobulin species

Download