Expression of Th1, Th2 and immunosuppressive cytokine gene transcripts in canine atopic dermatitis.
BACKGROUND
Atopic dermatitis is a common inflammatory skin disease of humans and dogs. Human atopic dermatitis is associated with Th2-type responses, although Th1 cytokines can be identified in chronic lesions. In contrast, tolerance to environmental allergens in healthy individuals is mediated by regulatory T cells.


OBJECTIVE
This study examined the expression of the immunosuppressive cytokines TGF-beta and IL-10, the Th2-type cytokines IL-4 and IL-6, and the Th1-type cytokines IFN-gamma, TNF-alpha, IL-2, IL-12p35 and IL-12p40, in canine atopic dermatitis.


METHODS
RNA was isolated from lesional atopic, non-lesional atopic and healthy canine skin samples. Semi-quantitative reverse transcriptase polymerase chain reactions (RT-PCRs) were carried out using specific primers and one-way analyses of variance used to compare cytokine expression in each group.


RESULTS
Canine atopic dermatitis was associated with over-expression of IL-4 mRNA and reduced transcription of TGF-beta compared with healthy skin (P < 0.05). Higher levels of IFN-gamma, TNF-alpha and IL-2 mRNA were seen in lesional compared with non-lesional and healthy skin (P < 0.05). There were no significant differences in IL-10, IL-6, IL-12p35 or IL-12p40 transcription between the three groups.


CONCLUSIONS
This is the first report to demonstrate that canine atopic dermatitis is associated with over-production of IL-4. Clinical tolerance in healthy individuals appears to be associated with TGF-beta, although it is unclear if this reflects an active mechanism or simply non-responsiveness of the immune system. Th1 cytokines may be induced by subsequent self-trauma and secondary infections in atopic skin. We believe that these results better characterize spontaneously occurring canine atopic dermatitis. We further propose that this should be investigated as a possible animal model of human atopic dermatitis.
Nuttall
T J
TJ
University of Edinburgh Department of Veterinary Clinical Science, Hospital for Small Animals, Easter Bush Veterinary Centre, Midlothian, UK. timn@liv.ac.uk
Knight
P A
PA
McAleese
S M
SM
Lamb
J R
JR
Hill
P B
PB
D000818:Animals; D016207:Cytokines / Q000235:genetics / Q000276:immunology*; D003876:Dermatitis, Atopic / Q000235:genetics / Q000662:veterinary*; D003877:Dermatitis, Contact / Q000235:genetics / Q000662:veterinary*; D004283:Dog Diseases / Q000235:genetics*; D004285:Dogs; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D016753:Interleukin-10 / Q000235:genetics / Q000276:immunology; D012333:RNA, Messenger / Q000378:metabolism*; D018417:Th1 Cells / Q000276:immunology* / Q000378:metabolism*; D018418:Th2 Cells / Q000276:immunology* / Q000378:metabolism*; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000276:immunology
D016207:Cytokines; D007166:Immunosuppressive Agents; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D016753:Interleukin-10