EARLY SIGNS OF ATOPY

• Doctors first noticed atopy with the success of vaccination in the early 1900’s, when doctors began injecting antigens and using immune serum. Numerous different phenomena were discovered at the time, that directed doctors to atopy and its pathogenesis.

• There were:
• discovery of serum sickness
• wheal-and-flare responses to injections (skin-prick test basis)
• passive transfer of skin-test sensitivity by serum from atopic individuals
• systemic anaphylaxis

 

• The serum factor that transferred skin-test sensitivity to allergens was discovered to be IgE. Allergen-specific IgE binds to mast cells, inflammatory cells found in the skin and lungs, through a high-affinity Fc receptor termed FceRI

• Allergens bind to these antibodies and cause crosslinking of these receptors, resulting in mast-cell degranulation and the release of many mediators of inflammation, such as histamine and prostaglandins. It is these factors that cold and allergy medications target to stop.

• IgE-mediated sensitivity is therefore considered central to atopy initiation

• IgE production by B cells depends on support from T helper 2 cells. This is in contrast to T helper 1 responses, which are created for cellular responses, such as seen in disorders such as Crohn’s and Psoriasis

References:

Kay AB. Allergy and allergic diseases. First of two parts. N. Engl. J. Med. 344, 30-37 (2001)
Kay AB. Allergy and allergic diseases. Second of two parts. N. Engl. J. Med. 344, 109-113 (2001)

Cookson W. The immunogenetics of asthma and eczema: A new focus on the epithelium. Nature Reviews Immunology 4, 978-988 (2004).