Innate immunity includes which of the following processes?

• A. Anamnestic response
• B. Antibody production
• C. Cytotoxic T cell activity
• D. Phagocytosis by polymorphonuclear cells

Answer: (D)

Innate immunity comprises immediate, non-specific defenses, including the ability of certain white blood cells to engulf and destroy pathogens. Phagocytosis by polymorphonuclear leukocytes (neutrophils) is a classic example. These cells patrol vessels and tissues, recognize generic features of pathogens, and quickly ingest them into a phagosome. The phagosome fuses with lysosomes to form a phagolysosome, where pathogens are killed and digested by reactive oxygen species, enzymes, and antimicrobial peptides. This rapid, antigen-non-specific process helps control infections before the adaptive system kicks in.

In contrast, anamnestic response reflects memory from prior exposure and is a hallmark of adaptive immunity. Antibody production is a product of the adaptive humoral response. Cytotoxic T cell activity is part of the adaptive cell-mediated response that requires antigen presentation and clonal expansion.