The key components of the immune system are thymus, bone marrow, secondary lymphatic tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, and the skin.
There are five types of white blood cells or leukocytes of which Lymphocytes are one off them. The most abundant lymphocytes are:
B lymphocytes (also known as the B cells or antibody producing cells) and T lymphocytes (also known as T cells).
The B cells have special significance as it is made where it matures in the bone marrow before leaving.
The immature T cells leave the bone marrow and mature in the thymus.
Thymus: The thymus is an lymph organ that is located in the center of the upper chest just behind the breastbone, the bone that connects the ribs. It is responsible for secreting cytokines capable for stimulating the production of T cells (lymphocytes) and their maturation responsible for cell-mediated immunity.
There are 3 types of T cells: Helper, Cytotoxic, Memory, Regulatory and Natural killer.
Helper T cells responsible for mediating inflammation.
Cytotoxic T cells responsible for killing cells infected with viruses.
Regulatory T cells responsible for mainstreaming the immune system and to induce tolerance for auto antigens.
Natural killer cells are cells responsible for killing tumor and virus infected cells.
Bone marrow: is the soft and sponge like tissue present in the hollow of bones. In adults, the bone marrow of larger bones are responsible for making new blood cells.
Immunoglobulins:
All antibodies are composed of 2 identical heavy polypeptide chains and 2 identical light chains shaped in the form of a Y. The groves of the 2 arms of the upper end of the Y are variable regions and is able to bind to specific antibodies. The variable region is called the (V) region and the part of the antibody that is constant is called the (C) region. Under inflammatory responses, B cells produce antibodies that are specific for a particular antibody. There are 9 classes of human immunoglobulins (Ig in short); 4 kinds of IgG and 2 kinds of IgA, plus IgM, IgE, and IgD.
