Which of the following is a primary mechanism by which the skin protects against infection by microbes?

• A. Production of antimicrobial peptides such as defensins
• B. Secretion of antibodies by keratinocytes
• C. Presence of high concentrations of glucose on the skin surface
• D. Active phagocytosis by skin epithelial cells

Answer: (A)

Verified step by step guidance

1. Understand the role of the skin as a physical and immunological barrier against microbial infection.
2. Recognize that keratinocytes, the primary cells in the epidermis, contribute to defense by producing antimicrobial peptides like defensins, which directly kill or inhibit microbes.
3. Evaluate the other options: secretion of antibodies by keratinocytes is not a primary function since antibody production is mainly by B cells, not skin cells.
4. Note that high concentrations of glucose on the skin surface are not typical and do not serve as a defense mechanism against microbes.
5. Understand that active phagocytosis is primarily performed by specialized immune cells (like macrophages), not by skin epithelial cells, so this is not a main protective mechanism of the skin.