Which immune cells are responsible for the first response to infection?

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

Answer: (B)

Neutrophils are the primary immune cells that respond first to infection. These cells are part of the innate immune system and are typically among the first responders to sites of inflammation or infection. They quickly move to the site of infection in response to signals such as chemokines released by damaged tissues or pathogens. Once there, neutrophils perform several protective functions, including phagocytosing (engulfing and digesting) bacteria and fungi, releasing enzymes, and producing reactive oxygen species to kill pathogens.

T cells and B cells, on the other hand, are part of the adaptive immune response, which takes longer to develop and requires prior exposure to a pathogen for effective action. Macrophages, although crucial in the immune response as well, are usually activated by neutrophils. They also play a role in cleaning up debris and presenting antigens to T cells, but they do not respond as quickly as neutrophils to a new infection. Thus, the rapid and effective response of neutrophils positions them as the critical first line of defense in the immune response to infection.