What are auto immune diseases ?

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An auto immune disease is a pathological attack of the body's immunity against one or several of its own tissues.   In simple words,  an auto immune disease is a self-destruction of one's own body.  Defense against foreign bodies is  important for survival.   People can be infected by four types of parasites,  mycotic (microscopic mushrooms such as in the typical vaginal infection), viral (Jacob-Creutzfeld's encephalitis is an example), bacteriological (as in certain of the more dangerous forms of meningitis) and protozoan (such as in malaria).   Let’s not even bother with actual animal species that can infest us as well.   In addition,  humans use the same complex network of body systems (the immune system, the blood-brain barrier) to prevent inanimate (non-living) substances from poisoning us, especially our favorite (or at least our most important) organ, the brain.  The importance of the brain is paid tribute to by the existence of a special network of cells which are specialized to block entry into the brain of all kinds of foreign and potentially harmful substances.  Of course,  most of these substances would be blood born.  Consequently,  it is at the junction of the tiny arterial vessels and the brain that we find the blood-brain barrier.  This barrier consists of special cells including glial cells (astrocytes) which filter out or block undesirable compounds.   In addition to this organ-specific barrier, several of the body's organs give birth to cells specialized in the war against these intruders,  the thymus, lymph nodes, bone marrow,  and spleen being the most important ones.   There are two main forms of defense against invaders (antigens),  humoral (liquids) and cellular (complete cells).   Immune cells are called lymphocytes.   It is these cells which, when out of control,  can actually attack either a specific tissue in an organ of the body,  or even several such tissues.   When such an attack is just a passing excessive irritating response to an antigen such as dog saliva, pollen or dust mites,  without permanent damage to the tissue exposed to the antigen,  then immunologists term the disorder an allergy.  The lymphocytes most involved in allergy are the IgE class.  These proliferate more and are more voracious in the human male child (not the adult).   Indeed, young boys are at higher risk for most allergies, but after adolescence women become more at risk than men.   However,  when lymphocytes attack one's own body tissue and destroy it,  then immunologists recognize the problem as an auto immune disease.  These auto immune diseases are caused by other types of lymphocytes.  Some auto immune diseases attack only one tissue rather selectively.  For example, multiple sclerosis involves a yellowing and hardening of the fatty white sheaths (myelin) enveloping neurons.  Some auto immune diseases affect numerous tissues in several organs of the body.  Behcet's disease causes oral and genital ulcerations and ocular keratitis (corneal inflammation), optic neuritis and uveitis (inflammation of the iris and choroid body of the eyeball).  The gastrointestinal, cardiovascular and central nervous systems, and joints and lungs are all under threat from this terrible disease.  Systemic lupus erythematosis is another multi-system auto immune disease. It was called lupus by a French doctor in the 19th century because the skin rash in this disease is so severe it resembles mauling by a wolf. It attacks and partially destroys skin, muscle, bone, kidneys, blood vessels, the heart, lungs, and the brain.  There used to exist a schism between immune pathology (infectiology) and auto immune pathology (rheumatology, etc.).   However,  it is now being claimed that many auto immune diseases,  though heavily hereditary,  may be triggered by specific infections,  which the body successfully combats.   Years later,  parts of the same immune system that saved the patients' life go haywire and turn against a specific tissue of the body, confusing it with a dangerous intruder.  Another interesting generality about auto immune disease is its capriciousness,  or the irregularity, heterogeneity, and waxing and waning of the symptoms.  I believe this is so because the delicate balance required of the immune system between killing every dangerous intruder and leaving one's own tissues intact,  varies from situation to situation.  For example,  immune demands change during childbearing and parturition,  during extreme stress, as a function of body temperature, etc.   Consequently,  the immune system relies on neural and endocrine signals to set its own balance.    These signals are variable and can be misinterpreted,  leading to apparent "capriciousness" of auto immune pathology. 

A vignette on a case with systemic lupus erythematosis (SLE)

In 1986,  Pollens published a clinical report of Mrs. C,   a 31 year-old woman with SLE.   Since the age of 21,  Mrs. C had been suffering from overwhelming fatigue,  severe photosensitivity        -developing into a painful rash in sunlight or fluorescent light,   severe pain resembling symptoms of arthritis,  and poor sleep.   She had received,  and then quit,  androgen steroid treatment causing her side effects including,  she said, hallucinations.    She was a tense, stoic, hard-working,  efficient mother and employee.    Psychotherapy was sought to help her learn to relax and some success was claimed to that end.

N.B.  In addition to the pathology described above,  common symptoms of SLE include  depression,  protein deposits in the kidneys leading to kidney failure,  psychosis (hallucinations and/or delusions),  cerebrovascular accidents (stroke), anemia,  carditis and cardiac arythmia (heart fluttering) and pleuritis (inflammation of the lungs).