The first immune cell type to respond when a finger wound is contaminated with Staphylococcus aureus is?

• A. B cells.
• B. Monocytes.
• C. Neutrophils.
• D. T cells.

Answer: (C)

The first immune cell type to respond to a contaminated finger wound is neutrophils, reflecting the rapid onslaught of the innate immune system to bacterial invasion. Neutrophils are stored in the bone marrow and released quickly when inflammatory signals are generated at the wound site. They migrate to the site by chemotaxis in response to signals such as chemokines, recognize bacteria through pattern‑recognition receptors, and rush in to phagocytose the invading Staphylococcus aureus. They also release antimicrobial granules and can form extracellular traps to contain and kill the bacteria, providing immediate, non-specific defense. B cells and T cells are part of the adaptive immune response and require antigen presentation and clonal activation, so they take longer to become involved. Monocytes arrive a bit later and differentiate into macrophages in tissues, contributing to ongoing phagocytosis and antigen presentation, but the earliest responders are neutrophils.