Type I or Anaphylaxis::
It is a swifit sudden and severe form of allergy occuring as a result of liberation of histamine and other substances these substances are released as a consequence of antigen and antibody reactions The antibodies IgE specifically bind to mast substances liberating histamine There is sudden fall in blood -pressure bronchial spasm and signs of shock including unconciousness Many drugs like penicillin or A.T.S. injection may cause anaphylactic shock
TYPE II or Cytotoxic type::
In this type of allergy antigen is localized on the surface of target cell (eg.blood cells) and the antibody present in the blood combines with antigen to cause the lysis of the target cell in this type of allergy there may occur haemolytic anaemia leucocytopenia or agranulocytosis or thrombocytopenia (blood dyscrasias) in this type IgG antibodies specifically take part The complement system also gets activated to phagocytose the cells and cause their lysis
TYPE III or Toxic -complex reaction :
This type of reaction occurs when there is sufficient amount of circulating antibodies The union of soluble antigen and antibodies in the body produce an actue inflammatory reaction The immune complex activates complement and releases anaphylitoxins and chemotactic factors Anaphylotoxins release histamine and increase vascular permeability The chemotactic factors cause an increase in leucocytes and phagocytosis The result of this type of allergy may be(1) Arthrus reaction and (2) serum sickness.In Arthrus reaction there is increase in antibodies that are produced as a sensitization to thermophilic actinomycets (fungi) There may be inflammatory reactions in respiratory system In serum sickness there is large amount of antigen Diphtheria or tetanus antibodies (used to produce passive immunity) may produce this type of reaction pyrexia (high fever) generalized edematous patches (urticaria) joint swelling and enlargement of lymph nodes this type of reaction takes about 7-10 days to develop
TYPE IV or Cell-mediated allergy::
This type of allergy is seen in response to bacteria viruses and fungi Antigen here directly involves T-lymphocytes Contact dermatitis and rejection of allergy In contact dermatitis there is redness swelling vesicles scaling and exudation of fluid
Various other disorders of immune disorders include :
(1) Rheumatoid arthritis
(2) Rheumatic fever
(3) systemic lupus erythromatosis
(4) Bamboo spine
(5) Myasthenia gravis
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