CLEP CLEP Biology Microbiology and Immunology 2 — Questions and Answers
Question 1: Which cells are responsible for producing and secreting antibodies?
- T helper cells
- Cytotoxic T cells
- Plasma cells (Correct answer)
- Natural killer cells
Correct answer: Plasma cells
Plasma cells are fully differentiated B lymphocytes that produce and secrete large amounts of antibodies specific to a particular antigen.
Question 2: What is the primary function of MHC Class I molecules?
- Presenting antigens to CD4+ T helper cells
- Presenting intracellular antigens to CD8+ cytotoxic T cells (Correct answer)
- Directly activating B cells
- Stimulating natural killer cells to divide
Correct answer: Presenting intracellular antigens to CD8+ cytotoxic T cells
MHC Class I molecules present intracellular peptide antigens to CD8+ cytotoxic T cells, signaling them to kill infected or cancerous cells.
Question 3: Which immunoglobulin class is most abundant in serum and is the only antibody that crosses the placenta?
- IgA
- IgM
- IgE
- IgG (Correct answer)
Correct answer: IgG
IgG is the most abundant serum antibody and crosses the placenta to provide passive immunity to the developing fetus and newborn.
Question 4: Which process allows developing B cells to generate highly diverse antibody specificities?
- Mitosis
- V(D)J recombination (Correct answer)
- Transcription
- DNA methylation
Correct answer: V(D)J recombination
V(D)J recombination randomly combines variable, diversity, and joining gene segments during B cell development to create diverse antigen-binding sites.
Question 5: Which complement pathway is activated by antibody-antigen complexes?
- Alternative pathway
- Lectin pathway
- Classical pathway (Correct answer)
- Properdin pathway
Correct answer: Classical pathway
The classical complement pathway is initiated when C1q binds to antibody-antigen complexes, triggering a proteolytic cascade that destroys pathogens.
Question 6: Vaccines confer protection primarily by:
- Killing pathogens before they enter the body
- Stimulating memory cell formation without causing disease (Correct answer)
- Increasing phagocyte activity in tissues
- Blocking pathogen entry at mucosal surfaces
Correct answer: Stimulating memory cell formation without causing disease
Vaccines introduce antigens to stimulate adaptive immunity and generate memory cells, enabling rapid, robust responses upon future exposure to the real pathogen.
CLEP CLEP Biology Microbiology and Immunology 2
Which cells are responsible for producing and secreting antibodies?