Sero-taxonomical classification of drugs MCQs With Answer

Serotaxonomical classification of drugs explores how antigen–antibody relationships and serological profiles inform pharmacology, vaccine design, and antibody-based therapeutics. For B.Pharm students, mastering serotypes, antisera, monoclonal and polyclonal antibodies, serological assays (ELISA, agglutination, precipitation, complement fixation), immunogenicity, and serum-related adverse effects is essential for rational drug development and clinical use. This classification links pathogen serotypes to targeted vaccines, guides antivenom and antitoxin production, and underpins diagnostic and sero-epidemiological strategies. Keywords: sero-taxonomical classification, serotype, antigen, antibody, antisera, monoclonal antibodies, vaccines, serology, immunotherapy, serum sickness. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What does sero-taxonomical classification of drugs primarily rely upon?

  • Patterns of antigen–antibody reactions and serological profiles
  • Chemical functional groups and molecular formulae
  • Pharmacokinetic parameters like half-life
  • Molecular weight and solubility

Correct Answer: Patterns of antigen–antibody reactions and serological profiles

Q2. A serotype is best defined as:

  • A strain of drug molecule with different chirality
  • A variant of a microorganism distinguished by surface antigens
  • A chemical class of antibiotics
  • A dosing regimen based on body weight

Correct Answer: A variant of a microorganism distinguished by surface antigens

Q3. How does serotyping influence vaccine formulation?

  • By identifying prevalent antigenic types to include in multivalent vaccines
  • By determining drug solubility for formulation
  • By selecting adjuvants based on pH only
  • By determining oral versus parenteral route exclusively

Correct Answer: By identifying prevalent antigenic types to include in multivalent vaccines

Q4. Which serological assay uses an enzyme-linked label to detect antigen–antibody binding?

  • Hemagglutination
  • Western blot
  • ELISA
  • Agglutination slide test

Correct Answer: ELISA

Q5. The observable principle behind agglutination tests is:

  • Color change produced by an enzyme substrate
  • Visible clumping due to antibody-mediated cross-linking of particles
  • Precipitate formation from soluble antigen–antibody complexes only
  • Radioactive labeling of antibodies

Correct Answer: Visible clumping due to antibody-mediated cross-linking of particles

Q6. In the complement fixation (CF) test, a positive antigen–antibody reaction is indicated by:

  • Extensive hemolysis of indicator red cells
  • No hemolysis because complement has been fixed
  • Immediate color change to blue
  • Formation of gas bubbles

Correct Answer: No hemolysis because complement has been fixed

Q7. Monoclonal antibodies differ from polyclonal antisera because monoclonals:

  • Recognize multiple different epitopes on an antigen
  • Are derived from whole-animal serum pools
  • Are identical antibodies produced from a single hybridoma and target one epitope
  • Always cause serum sickness more frequently

Correct Answer: Are identical antibodies produced from a single hybridoma and target one epitope

Q8. Which of the following is an example of passive immunization used clinically?

  • Administration of an inactivated vaccine
  • Administration of antivenom or human immunoglobulin
  • Oral polio vaccine given to induce long-term immunity
  • Administration of adjuvant alone

Correct Answer: Administration of antivenom or human immunoglobulin

Q9. Serum sickness is classically categorized as which type of hypersensitivity?

  • Type I (immediate, IgE mediated)
  • Type II (antibody-dependent cytotoxic)
  • Type III (immune complex mediated)
  • Type IV (delayed, T-cell mediated)

Correct Answer: Type III (immune complex mediated)

Q10. A viral neutralization assay primarily measures:

  • The ability of antibodies to agglutinate red cells
  • The capacity of antibodies to prevent viral infectivity of host cells
  • Complement levels in serum
  • Antibody molecular weight distribution

Correct Answer: The capacity of antibodies to prevent viral infectivity of host cells

Q11. Sero-epidemiology is important because it:

  • Measures drug solubility in populations
  • Assesses the prevalence of specific antibodies or exposure in a population
  • Determines the pharmacokinetics of monoclonal antibodies
  • Replaces microbiological culture entirely

Correct Answer: Assesses the prevalence of specific antibodies or exposure in a population

Q12. Hemagglutination inhibition (HI) tests are used to detect antibodies that:

  • Enhance complement-mediated lysis
  • Block viral hemagglutinin and prevent agglutination of red cells
  • Bind to bacterial cell walls only
  • Directly cleave antigens enzymatically

Correct Answer: Block viral hemagglutinin and prevent agglutination of red cells

Q13. In a complement fixation test, the absence of hemolysis indicates:

  • There was no antibody in the test serum
  • Complement was fixed by antigen–antibody complexes indicating a positive reaction
  • Complement was inactivated due to heat and test is invalid
  • Antigen concentration was too low to react

Correct Answer: Complement was fixed by antigen–antibody complexes indicating a positive reaction

Q14. Which serological method is most suitable for quantitative measurement of antibody concentration?

  • Slide agglutination only
  • ELISA with a standard curve
  • Simple precipitation on a glass slide
  • Direct microscopy

Correct Answer: ELISA with a standard curve

Q15. Antivenoms described as polyvalent mean they:

  • Contain antibodies against multiple venoms or toxins
  • Are effective only against a single venom
  • Are synthetic small-molecule inhibitors
  • Are always monoclonal antibody preparations

Correct Answer: Contain antibodies against multiple venoms or toxins

Q16. Which animal is commonly used for large-scale production of therapeutic antisera (antivenoms, antitoxins)?

  • Guinea pig
  • Horse
  • Mouse
  • Chicken

Correct Answer: Horse

Q17. A major limitation of sero-taxonomical classification is:

  • Absolute specificity with no cross-reactivity
  • Cross-reactivity between related antigens that can confound results
  • Its inability to detect antibodies at any concentration
  • The requirement for radioactive reagents only

Correct Answer: Cross-reactivity between related antigens that can confound results

Q18. The term ‘avidity’ of an antibody refers to:

  • The strength of a single antigen–antibody bond
  • The cumulative strength of multiple binding interactions between multivalent antibody and antigen
  • The molecular weight of the antibody
  • The ability to fix complement only

Correct Answer: The cumulative strength of multiple binding interactions between multivalent antibody and antigen

Q19. Hybridoma technology is used to:

  • Produce polyclonal antisera in rabbits
  • Generate monoclonal antibodies by fusing B cells with myeloma cells
  • Synthesize small-molecule drugs chemically
  • Isolate complement proteins from serum

Correct Answer: Generate monoclonal antibodies by fusing B cells with myeloma cells

Q20. The suffix ‘-mab’ in a drug name indicates the molecule is:

  • An antiviral small molecule
  • A monoclonal antibody therapeutic
  • A vaccine antigen
  • A chemotherapeutic alkylating agent

Correct Answer: A monoclonal antibody therapeutic

Q21. One advantage of polyclonal antisera over monoclonal antibodies is:

  • Recognition of a broader range of epitopes on the same antigen
  • Unlimited batch-to-batch consistency
  • Absolute lack of cross-reactivity
  • They are always human-derived and non-immunogenic

Correct Answer: Recognition of a broader range of epitopes on the same antigen

Q22. International Units (IU) are commonly used to express potency of:

  • Small-molecule antibiotics only
  • Antitoxins and antisera biological activity
  • pH of vaccine formulations
  • Volume of serum administered

Correct Answer: Antitoxins and antisera biological activity

Q23. Which serological test produces a precipitin line by diffusion of soluble antigen and antibody?

  • Agglutination test
  • Precipitation (Ouchterlony) test
  • Hemagglutination inhibition
  • Western blot

Correct Answer: Precipitation (Ouchterlony) test

Q24. Which immunoglobulin class is the earliest serological marker of recent infection?

  • IgG
  • IgM
  • IgA
  • IgE

Correct Answer: IgM

Q25. A characteristic of passive immunotherapy is that it:

  • Requires weeks to confer protection
  • Provides immediate protection that is short-lived
  • Induces long-lasting memory B cells
  • Always eliminates the need for vaccines

Correct Answer: Provides immediate protection that is short-lived

Q26. Which immunoglobulin plays a primary role in mucosal immunity and is abundant in secretions?

  • IgG
  • IgM
  • IgA
  • IgD

Correct Answer: IgA

Q27. For short-term storage and stability of therapeutic antisera, the recommended refrigeration temperature is typically:

  • -80 °C (deep freeze)
  • 2–8 °C (refrigeration)
  • Room temperature 20–25 °C
  • Boiling point to inactivate contaminants

Correct Answer: 2–8 °C (refrigeration)

Q28. Cross-reactivity in serological tests occurs when:

  • Antibodies bind strictly to a single unique epitope
  • Antibodies bind to similar epitopes on different antigens
  • Antigens are completely unrelated chemically
  • Only monoclonal antibodies are used

Correct Answer: Antibodies bind to similar epitopes on different antigens

Q29. Serotyping of Streptococcus pneumoniae is clinically important because:

  • All serotypes respond identically to every antibiotic
  • Capsular serotype determines inclusion in pneumococcal vaccines
  • It determines viral resistance patterns
  • It is used only for fungal pathogens

Correct Answer: Capsular serotype determines inclusion in pneumococcal vaccines

Q30. The risk of serum sickness is higher with which type of therapeutic serum?

  • Fully human monoclonal antibodies only
  • Heterologous animal-derived antisera (e.g., equine antivenom)
  • Recombinant human proteins with human glycosylation
  • Autologous plasma transfusions

Correct Answer: Heterologous animal-derived antisera (e.g., equine antivenom)

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