A 65-year-old man with a past medical history of well-controlled hypertension on lisinopril presents for annual preventive care. He reports feeling well with no acute complaints. Vital signs are stable and physical examination is unremarkable. Laboratory studies reveal normal complete blood count, comprehensive metabolic panel, and lipid panel. Compared to a healthy 20-year-old, this patient's immune system has most likely undergone which of the following age-related changes?

1. A)Increased number of naive T cells with preserved thymic output
2. B)Increased affinity maturation of antibodies due to expanded germinal center reactions
3. C)Decreased antibody response to new vaccines and impaired T cell-mediated immunityGABARITO
4. D)Increased production of complement proteins with enhanced opsonization
5. E)Decreased prevalence of autoimmune phenomena due to improved immune regulation