Lymphatic System

Lymphocytes are the lymphatic system's foot soldiers. These cells identify enemy particles and attempt to destroy them. Lymphocytes fall into two general categories: T lymphocytes (T cells) and B lymphocytes (B cells). T cells form in the thymus (in the chest), and B cells form in the bone marrow of the long, thick bones of the thigh, arm, spine, or pelvis. While T cells primarily attack viral antigens, B cells attack bacterial antigens. Both T and B cells travel in lymph, through lymphatic vessels, and into lymph nodes.

T cells are further divided into three primary classes: helper T cells (T-H cells), cytotoxic T cells (ctx T cells), and T suppressor T cells. T-H cells augment B cell responses to bacterial antigens. Cytotoxic T cells attack viral antigens and some early cancer cells. And suppressor T cells halt immune cell functions, allowing the body to rest.

B cells produce antibodies. According to their basic immunoglobulin type, antibodies are subdivided into five classes (IgM, IgD, IgG, IgE, and IgA). B cell antibodies recognize specific bacterial invaders and destroy them. Certain antibodies are more concentrated in areas of the body where they are most needed. For example, IgA-producing B cells are most concentrated in the Peyer's patches where they sample intestinal contents for potential antigens that could signal an infectious invasion of food-borne bacteria.