Christopher:
Bacterial antigens are probably not important in the genesis of IgE mediated
diseases because of the route of sensatization. The factors influencing the
commitment of TH0 cells to becoming a TH1 type cell (Responsible for CTL
responses mainly) or TH2 type cell (responsible for humoral immune response,
esp. IgE) are still unclear but probably include the type of antigen presenting
cells, the strength of antigen-MHC-TCR interaction etc. Antigens known to
elicit a TH2 response in the airways (eg. the dust mites Dermatophygoides
Farinae or Pteronysinnus) can elicit a TH1 type response when given
subcutaneously (The basis of the Allergy Shots). Staphylococcal superantigens
have been implicated in the genesis or perpectuation of eczema, but this is of
course a type IV immune response.
Helminthic infections, however, are very strong stimulants for IgE responses.
Patients with certain helminthic infections can develope asthma like symptoms
and urticaria, and sometimes pulmonary eosinophilia. Certain respiratory
viruses have also been implicated in childhood asthma. Some studies have shown
the presence of IgE specific for Respiratory Syncitial Virus, adenovirus and
parainfluenza virus in the serum of asthmatic children, and such virus
infections are known to exacerbate asthma. Better studies need to be done
however, to verify these findings. Virus infections can also cause acute
urticaria, but the mechanisms are unknown.
Adrian Wu M.D.
Department of Immunology
The Scripps Research Institute
La Jolla, CA
(619)554-2195