Correct option is A
- A. Cells that have switched to IgG1 may undergo further switching to IgA – This is correct, as class switching can proceed from IgG1 to IgA.
- D. The progeny of proliferating cells may undergo independent switching events – This is also correct, as clonal expansion results in progeny cells that can independently undergo further switching to different isotypes.
The combination of A and D best fits the experimental observations.
Information Booster:
- Class Switching: B cells can change the antibody isotype they produce through class switching, allowing different antibodies like IgG1, IgA, etc., to be produced while maintaining antigen specificity.
- IgA and IgG1 Switching: Once a B cell has switched to IgG1, it may further switch to IgA depending on cytokine signals. This is common in mucosal immunity.
- Simultaneous Secretion: Although B cells can sometimes co-express multiple antibodies, simultaneous secretion of both IgG1 and IgA is rare and not directly supported by the experiment.
- Progeny and Independent Switching: As B cells proliferate, their progeny may undergo independent switching events, leading to different antibody profiles in a single population of cells.
- Immunoglobulin Diversity: Class switching contributes to the diversity of the immune response, ensuring that a broader range of immune challenges can be addressed.
- Clonal Expansion and Differentiation: B cells undergo clonal expansion after activation, with each progeny cell potentially undergoing independent class switching.
Additional Information:
Incorrect Option B (Cells that have switched to IgA may undergo further switching to IgG1): This statement is inconsistent with the experiment. The experiment found that cells switching to IgG1 could further switch to IgA, but not the reverse.
Incorrect Option C (A single cell can simultaneously secrete IgG1 and IgA): This statement is incorrect in the context of the experiment, which does not show definitive evidence of simultaneous secretion by the same cell.
