Determination of the T cell epitopes of the lipocalin allergen, Rat n 1.
BACKGROUND
Laboratory animal allergy (LAA) is an important cause of occupational sensitization and asthma. Rats are a frequent cause of LAA and the major rat allergen, Rat n 1, is a member of the lipocalin protein family, which includes several other animal allergens such as the cow allergen, Bos d 2. To date, Bos d 2 is the only mammalian lipocalin allergen to have been studied in detail.


OBJECTIVE
We undertook a cross-sectional study of a large population of individuals exposed to laboratory rats to determine the proliferative responses of peripheral blood mononuclear cells (PBMCs) to the major rat allergen, Rat n 1.


METHODS
Eighty-three cases (defined by a positive skin prick test (SPT) > or =3 mm and/or a positive RAST > or =2% binding) and 274 referents without specific IgE to rats were tested for their proliferative responses of PBMCs to rat allergen. Cytokine release to rat urinary protein was examined in 28 sensitized and 42 non-sensitized exposed individuals.


RESULTS
Proliferation to rat urinary protein was weak in all individuals. Four regions within Rat n 1 were identified as containing potential immunodominant T cell epitopes and three of these co-localized within the conserved regions of the lipocalin molecule. All four regions within Rat n 1 overlapped considerably with the characterized epitopes of the lipocalin allergen, Bos d 2. IL-5 and ratios of IL-5/IFN-gamma were significantly increased in cases.


CONCLUSIONS
The response to Rat n 1 is remarkably similar to the cow lipocalin allergen Bos d 2. T cell epitopes within lipocalins appear to co-localize with the conserved regions of the molecule. LAA is characterized by an increased production of IL-5. Investigation of other lipocalin allergens will provide further information about the allergenicity of this group of proteins.
Jeal
H
H
Department of Occupational and Environmental Medicine, Imperial College, London SW3 6LR, UK.
Draper
A
A
Harris
J
J
Taylor
A Newman
AN
Cullinan
P
P
Jones
M
M
D000485:Allergens / Q000276:immunology*; D017750:Animal Technicians; D000818:Animals; D016022:Case-Control Studies; D049109:Cell Proliferation; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D000939:Epitopes / Q000032:analysis*; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000175:diagnosis / Q000276:immunology*; D007073:Immunoglobulin E / Q000097:blood; D015848:Interleukin-5 / Q000276:immunology; D008213:Lymphocyte Activation; D009784:Occupational Diseases / Q000175:diagnosis / Q000276:immunology*; D016273:Occupational Exposure; D051381:Rats; D012882:Skin Tests; D013601:T-Lymphocytes / Q000276:immunology*
D000485:Allergens; D000939:Epitopes; D015848:Interleukin-5; C472325:n 1 allergen, rat; D007073:Immunoglobulin E