Part one of term paper
is a group of cells, molecules, and tissues that help defend the body against diseases and other harmful invaders. provides protection against a variety of potentially damaging substances that can invade the body. These substances include disease-causing organisms, such as bacteria, fungi, parasites, and viruses. The body's ability to re ...

Part two of term paper
... is composed of many parts that work together to fight infections when pathogens or poisons invade the human body. Pathogens are disease-causing organisms such as bacteria and viruses. The immune system reacts to foreign substances through a series of steps know as the immune response. Any agent perceived as foreign by a body's immune system is called an antigen. Several types of cells may be involved in the immune response to antigens. When an antigen enters the body, it may be partly neu ...