Many species have two major subsystems of the immune system. The innate immune system provides a preconfigured response to broad groups of situations and stimuli. The adaptive immune system provides a tailored response to each stimulus by learning to recognize molecules it has previously encountered.
Your immune system is a network of organs, white blood cells, proteins and chemicals that work together to protect you from invaders (like germs) that can harm you.
The immune system is a group of defense responses found in humans and other advanced vertebrates that helps repel disease-causing entities. Immunity from disease is conferred by two cooperative systems: innate immunity and acquired (or adaptive) immunity.
The immune system works to keep germs and other foreign substances out of the body and destroy any that get in. It's made up of a complicated network of cells and organs.