A part of immune system in our body protects us from the self-reactive immune complexes. When this regulatory mechanisms functions abnormally, self-reactive auto-immune complexes are formed which acts against the normal immune-protective system. Autoimmunity was first described by Paul Ehlrich during the first of 20th century.

Self-reactive immunologic components are normally suppressed in normal individual by clonal anergy or clonal suppression. Irregularities in clonal anergy lead to the activation of self-reactive immune components. These self-reactive immune complexes generate humoral or cell mediated response against self-antigenic components. This in turn leads to autoimmune diseases.

When self-reactive immune complexes act against a broad range of target antigens and affect a number of organs and tissues systemic autoimmune diseases occur. An irregularity in immune regulation results in hyperactive T and B cells. These results in a widespread tissue damage both from cell-mediated immune responses and from direct cellular damage caused by auto-antibodies or by accumulation of immune complexes. Some of the systemic auto-immune diseases are as follows.

A. Systemic Lupus Erythematosus

Systemic lupus erythematosus or SLE is the best example of a systemic auto-immune disease. It is most prevalent in women in the range of 20 to 40 years of age. The symptoms of SLE are fever, weakness, arthritis, skin irritation, pleurisy and renal disorders. SLE is found to be more prevalent in African-American and Hispanic women than others such as Caucasians. The particular reason for this prevalence in disease among a particular class of women is still unknown.

A person suffering from SLE produces auto-antibodies to a vast range of tissue antigens like DNA, histone, RBCs, platelets, leukocytes and blood coagulation factors. Interaction of these auto-antibodies with tissue antigens gives rise to the auto-immune disease symptoms. Auto-antibodies targeting RBCs and platelets lead to haemolytic anaemia and thrombocytopenia. A type III hypersensitivity reaction is produced when auto-antibodies are deposited on the walls of the small blood vessels. It damages the blood vessel walls are attacked by membrane-attack complexes and complement split products. Another characteristic of this disease is that the neutrophils gets attach to the blood vessel walls resulting in a sharp decrease in the neutrophil level in circulating blood. These damages to blood vessel walls lead to vasculitis and glomerulonephritis.

B. Multiple Sclerosis

Multiple sclerosis or MS is a disease that attacks and degrades the central nervous system of an individual. In western countries it is the most prevalent cause of neurologic disorders. MS mostly occur in people in the age range of 20 to 40 years. Basic characteristic of the disease is numbness in limbs. In severe stages the symptoms are like paralysis or loss of vision. MS affects women 2 to 3 times more than men.

Patients suffering from MS produce self-reactive T cells that form inflammatory lesions along the myelin sheath of the nerve fibres. The myelin sheath acts as insulation to the nerve fibres. A self-reactive T cell rich cerebrospinal fluid travels within the brain tissue and cause inflammatory lesions in myelin sheath. A progressive degradation in myelin sheath leads to several neurologic disorders.

C. Scleroderma

Scleroderma means "hard skin". In this type of systemic auto-immune disease skin is affected locally at first. In more severe form the disease spreads to the internal organs and the vasculature. The common symptoms of scleroderma are gradual tightening of the skin, usually in the outer part of the body like hands, feet and face.

The first characteristics of the disease is hardening of the exterior parts of the skin especially in face and hands. In the severe form of the disease patients develop five symptoms of the disease called CREST in abbreviation. CREST syndrome stands for calcinosis, Reynaud's phenomenon, esophageal dysfunction, sclerodactyly and telangiectasia. Calcinosis means a painful calcium deposition. In Reynaud's phenomenon abnormality in blood flow occurs in response to cold or stress. In esophegal dysfunction problems with swallowing occur. Tightening of the skin occurs in sclerodactyly and red spots are formed on the hands, palms, forearms, face and lips. In more severe form of this disease, internal organs like kidneys, lungs, heart, gastro-internal tract and joints get attacked leading to a premature death.

D. Rheumatoid Arthritis

This systematic auto-immune disease occurs mainly in women from 40-60 years of age range. The major characteristic of this disease are chronic inflammation of the joints. Individuals suffering from rheumatoid arthritis produce a group of auto-antibodies called rheumatoid factors that are self-reactive with determinants in the Fc region of IgG. Rheumatoid factor is basically an IgM antibody. These auto-antibodies bind to normal circulating IgG, forming IgG-IgM complexes that get deposited in the joints. These abnormalities in immune functions activate a complement cascade which leads to a type III hypersensitive reaction. This type III hypersensitive reaction results in an acute inflammation of the joints.

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