Host Defense Mechanisms 

We live in a world dominated by microbes

The atmosphere is full of bacteria,viruses, molds and parasite

? What mechanisms prevent infections

The discipline of immunology emerged out of the observation that

Individuals who had survived from certain

infectious diseases were there after protected from the disease

The Latin term immunis, meaning “exempt,” is the source of the English word immunity meaning the state of  protection from infectious disease

These observations marked the beginnings of the discipline of immunology

The term : Immunity

refers to the state of protection from

infectious disease

:and the discipline is called

Immunology

The Immune System is Organized into Two Main Branches 

The Natural (innate) or non-specific

.immune system

 The adaptive (acquired) or specific immune system

the two systems work together to provide protection