Immune system in your body
Human immune system is composed of a network of cells, tissues, and organs that work together to protect the host against the bacterial, parasitic, fungal, viral infections and from the growth of tumor cells (Linnemeyer 2008). There are two categories of human immune systems - innate immune system and acquired immune system. The physical barriers (such as the skin, saliva, mucus, hair and cilia) which is part of the innate immune system prevent and destroy the microbes penetrating inside the cells.
If the invaders overcome the innate immune system, they are met by the acquired immune system. The key players of the innate acquired system are the T-cells (originated from thymus) and B-cells (originated from bone marrow). B cells is responsible for producing antibody which is found in blood. They bind to and kill the pathogens that are outside of a cell. T-cells are responsible for directly killing the infected cells, as a result stopping the replication of the pathogens. One sub types of T-cells called the helper T cells (CD4 cells). These cells are critical in maintaining and the activity of the immune system because they are responsible in helping either B cells or T cells (Brown 1995). |