Final answer:
Alpha defensins are secreted in the intestines while beta defensins are expressed in the skin and respiratory tract.
Step-by-step explanation:
Alpha and beta defensins are small cysteine-rich cationic proteins that are important components of the innate immune system. They are secreted by neutrophils and epithelial cells and are known to be present at various body sites. Alpha defensins are primarily secreted by neutrophils and intestinal Paneth cells, contributing to the immune response in the intestines. On the other hand, beta defensins are expressed in a variety of epithelial cells, particularly in the skin and the respiratory tract. Therefore, the correct answer to the question 'Where are alpha and beta defensins secreted?' is C) Skin - Respiratory tract.