25.9 : 自然免疫と獲得免疫の概要

Present from birth, innate immunity is the body's first line of defense against a wide range of harmful pathogens.

It provides immediate, non-specific protection relying on physical and chemical barriers.

Physical barriers such as skin and mucus membranes provide a first line of defense against pathogen entry.

When these barriers are breached, the second line of defense comes into play, featuring antimicrobial peptides, phagocytes, and other immune cells.

Together, they eliminate the invaders and prevent their spread throughout the body.

Unlike innate immunity, adaptive immunity offers a more targeted response and develops over time through exposure to different pathogens. It is specific, systemic, and retains memory of the pathogen.

Adaptive immune responses can be categorized into cell-mediated or antibody-mediated responses.

The cell-mediated response engages T lymphocytes, which directly target and destroy infected or cancer cells.

The antibody-mediated response activates B lymphocytes, which produce antibodies.

These antibodies identify and mark pathogens for destruction by other immune cells.