Which statement accurately describes aging effects on immune function in dogs?

• A. It increases immune function
• B. It decreases immune function
• C. It has no effect
• D. It fluctuates unpredictably

Answer: (B)

Aging leads to a decline in immune competence, a process called immunosenescence. In older dogs, the thymus undergoes involution, producing fewer naive T cells and weakening cell-mediated immunity. B cell function and antibody production can also wane, so responses to vaccines and new infections may be less robust. Wound healing can be slower, and the overall risk of infections and cancer rises. While there can be some individual variation, the general trend with age is a decrease in immune function rather than an increase or no change.