Immunophenotype and Interleukin-17 Expression in Dogs with Immune Mediated Hematologic Disease

Abstract:

Background: Pathogenesis of canine immune mediated hematologic diseases, such as immune mediated hemolytic anemia (IMHA) and thrombocytopenia (ITP) is poorly understood. Changes noted in people with immune mediated diseases include deficient T regulatory cells, dysregulation of T cells, and excessive proinflammatory responses.

Objectives: The objective of this study was to describe the prevalence of selected T cell populations and interleukin (IL)-17 producing cells in dogs with IMHA and ITP. Animals: Blood samples were collected prior to treatment from 15 healthy control dogs and 15 dogs with newly diagnosed non-associative IMHA or ITP.

Methods: Samples were stained with antibodies against extracellular CD4, CD8, CD25 and intracellular IL-17 and Foxp3. Flow cytometry analysis was used to characterize lymphocytes.

Results: Compared with healthy dogs, dogs with immune mediated hematologic disease had significantly lower frequency of CD4+ (median 17%, range 3.96-34 versus 5.87%, 1.28-39.3, p=0.0495) and CD8+ (median 9.54%, range 3.75-31.1 versus 0.81%, 0.19-4.26, p<0.001) lymphocytes. CD4+CD25+Foxp3 T regulatory cells were significantly higher in dogs with immune mediated hematologic disease compared to healthy dogs (median 1.94%, range 0.23-13.5 versus 0.56%, 0-7.43, p=0.0028). Interleukin-17 positivity was significantly higher in lymphocytes of dogs with immune mediated hematologic diseases compared to healthy dogs (median 0.71%, range 0.09-4.92 versus 0.20, 0.03-0.63; p=0.0024). 
Conclusions and clinical importance: A deficiency in CD4+CD25+Foxp3 T regulatory cells was not observed in dogs with immune mediated hematologic disease. The low frequency of CD4+ and CD8+ cells suggests T cell dysregulation in dogs with immune mediated hematologic disease. Increased production of the pro-inflammatory cytokine IL-17 may contribute to the pathogenesis of canine immune mediated hematologic disease.