Introduction to Immune System

The human body is constantly exposed to a variety of external elements. These foreign materials find their way into the body via inhalation, ingestion, and penetration. As we inhale to get our required oxygen from the air, we also inhale fumes, smoke, dust, pollens, particles, molds, bacteria, viruses, and their by-products. Another way we expose our bodies to foreign invaders is through trauma and injury. The system responsible to defend us against these foreign substances is our immune system, and our protective status, natural or acquired, is known as immunity. The two types of immunity are innate immunity and acquired or adaptive immunity.