The Immune System of the Human Body

The Immune Syste= m of the Human Body

The Immune System is a defense system against invaders and infectio= us organisms. Disease is all aro= und you. It is everywhere. This system consists of cells, tis= sues and organs that work to together to protect the body from invaders and dise= ase. When your immune system is at work= you may feel the symptoms of fever, swelling, or runny nose. This is how you know you immune sy= stem is at work. The immune systems works with the circulatory system for transportation and the lymphatic syst= em to produce lymphocytes.

The White Blood Cells called leukocytes are part of the immune system. Leukocytes are made and stored in different places in the body such as the thymus, spl= een, bone marrow, lymph nodes throughout the body house leukocytes. Leukocytes circulate through aroun= d the body between the organs and nodes through the lymphatic vessels and through blood vessels. There are two = types of leukocytes.

Types of Leukocytes:

The phagocytes engulf and digest invading organisms. One type = of

= p= hagocyte is a neutrophil. Increased numbers of these cells i= n the

= b= lood indicates an infection is present.

The lymphocytes are memory cells t= hat remember and recognize past invaders.

= T= wo types of lymphocytes are B lymphoc= ytes and T lymphocytes. &n= bsp; = ; &= nbsp; Lymphocytes start out in the bone marrow and become B lymphocytes or &= nbsp; &nbs= p; go to the thymus gland and become T lymphocytes. B lymphocytes find

= t= heir target and then send defenses to attack invaders. T cells are

= t= he destroyers of invaders.

An Antigen is an invader of the body. The immune system detects the pres= ence of antigens. B lymphocytes ma= ke Antibodies. Antibodies are special proteins and attach to the antigens like a key and a lock. The antibodies stay in your body t= o give you immunity the next time the invaders enter. The T cells (killer cells) destroy= the antigens that have been tagged with antibodies.

The Organs of the Immune System:

Bone Marrow -- All the cells of the immune system are initial= ly derived from the bone marrow. The bone marrow prod= uces B cells, natural killer cells, granulocytes and immature thymocytes, in addit= ion to red blood cells and platelets.

Thymus --<= /b> The thymus produces mature T cells. Immature thymocytes, also known as prothymocytes, leave the bone marrow and migrate = into the thymus. The mature T cell= s are then released into the bloodstream.

Spleen --<= /b> The spleen is filter of the blood. It is made = up of B cells, T cells, macrophages, dendritic cells, natural killer cells and red blood cells. The spleen captures foreign antigens from the blood that passes through the spleen, migratory macrophages and dendritic cells bring antigen= s to the spleen via the bloodstream. Old red blood cells are destroyed in the spleen.

Lymph Nodes -- The lymph nodes function as a filter for the b= odily fluid called lymph. Lymph nodes are found throughout the body and are made = of mostly of T cells, B cells, dendritic cells and macrophages. The nodes drain fluid from most of= our tissues. Antigens are filtered out of the lymph in the lymph node before returning the lymph to the circulation.

However, the Immune = System can sometimes make mistakes and cause autoimmune diseases. These diseases, = such as lupus, are caused when the Immune System attacks its own cells and tissu= es.

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