Date posted: November 29, 2011  When adaptive immune response
occurs in an exaggerated or inappropriate form, the term
hypersensitivity is applied. Hypersensitivity reactions are the
result of normally beneficial immune responses acting
inappropriately and sometimes cause inflammatory reactions and
tissue damage. Many antigens can provoke hypersensitivity. The
causes of hypersensitivity reactions vary from one individual to
the next. Hypersensitivity is not manifested on the first
contact with the antigen but appears on subsequent contact.
Coombs & Gell classified four types of Hypersensitivity i.e.,
Types I,II,III,&IV., But in practice these types do not
necessarily occur in isolation. The first three are antibody
mediated; T cells & macrophages mediate the fourth.
–Anaphylactic type Prototype disorder – Anaphylaxis, some forms
of bronchial asthma, hay fever, eczema. Immune mechanism –
Formation of Ig E ( Cytotrophic antibody) leads to release of
vaso active amines and other mediators from basophils and ma