How does aging typically affect a dog's immune function?

• A. Increases
• B. Decreases
• C. No change
• D. Improves

Answer: (B)

Aging in dogs generally leads to a decline in immune function, a pattern called immunosenescence. The adaptive immune system loses vigor as the thymus shrinks, reducing the production of naive T cells and narrowing the ability to respond to new infections or vaccines. B cell function and antibody production can also diminish, meaning vaccines may not provoke as strong or as durable a response. Innate immune components aren’t entirely spared either; neutrophil function and macrophage activity can become less efficient, and there’s often a background of chronic, low-grade inflammation (inflammaging) that contributes to tissue damage and age-related disease. Taken together, these changes make older dogs more susceptible to infections, slower to heal wounds, and with less robust responses to vaccination.