Which cells perform phagocytosis in nonspecific immunity?

• A. Phagocytes, including neutrophils and macrophages
• B. Lymphocytes and plasma cells
• C. Erythrocytes and platelets
• D. T helper and cytotoxic T cells

Answer: (A)

Phagocytosis is a hallmark activity of the innate (nonspecific) immune response, carried out by phagocytes. Neutrophils are the first responders that rapidly move toward infection sites and engulf bacteria, while macrophages reside in tissues and can ingest larger particles, dead cells, and microbes. The process begins with chemotaxis toward signals from pathogens or damaged tissue, followed by attachment to the microbe (often enhanced by opsonins like antibodies or complement), ingestion into a phagosome, and digestion inside lysosomes using enzymes and reactive oxygen species. This mechanism is nonspecific because it targets a broad range of invaders without prior exposure or antigen-specific receptors.

Lymphocytes and plasma cells, by contrast, belong to the adaptive immune system and focus on antigen-specific responses, including antibody production and targeted cell-mediated actions; they are not primarily phagocytes. Erythrocytes and platelets do not perform phagocytosis as a main function, and T helper and cytotoxic T cells are lymphocytes that coordinate and execute specific immune responses rather than engulfing particles.