Detection of anti-erythrocyte antibodies in dogs with immunosuppressant-responsive enteropathy (IRE)

Immunosuppressant-responsive enteropathy (IRE) is a chronic gastrointestinal inflammation with a significative immune system involvement. Several extra-intestinal manifestations are reported in human IBD, including immune-mediated cytopenias, while they are not documented in dogs. The aim of the study was to evaluate the erythrogram, as part of complete blood count (CBC), and the presence of anti-erythrocyte antibodies in dogs with IRE. IRE was diagnosed with the following criteria: chronic gastrointestinal signs, no improvement with diet trial, evidence of inflammatory infiltration on intestinal histology and subsequent improvement after immunosuppressant therapy. Canine Chronic Enteropathy Activity Index Score (CCECAI) was recorded for each dog, as well as WSAVA endoscopic and histopathological score. Each dog had a CBC evaluation prior the endoscopic procedure as part of the routine care. CBC was performed using Procyte® Hematology analyzer (IDEXX Laboratories) and blood smears were reviewed by a single clinical pathologist and the presence of nucleated RBC (nRBCs), anisocytosis, polychromasia, and Howell-Jolly bodies was recorded. Anti-erythrocyte antibodies (IgG) were evaluated on the same blood sample with flow cytometry (Cytomics FC 500 Beckman Coulter®). The presence of anti-erythrocyte antibodies was associated with CCECAI score, endoscopic and histological score of IRE dogs using Chi-square test. Seventeen dogs with IRE were enrolled. Eight out of 17 dogs (47%) had anemia which was normocytic normochromic (62%), followed by microcytic normochromic (25%) and macrocytic normochromic (13%). The main alterations in blood smears were: presence of nucleated RBC (57.1%), anisocytosis (42.9%), polychromasia (28.6%), and Howell-Jolly bodies (28.6%). Anti-erythrocyte antibodies were revealed (IgG>0.2%) in 70.6% of the study population and in 87.5% of anemic dogs, although they were not statistically associated with CCECAI, endoscopic and histopathological score. The present study revealed a high frequency of positive cases for anti-erythrocyte antibodies in dogs with IRE. Moreover, about the half of the entire population study showed some hematologic features of RBC regeneration (e.g., polychromasia, NRBCs, anisocytosis) in addition to chronic inflammation hematologic findings (e.g., microcytemia). Although prospective, larger-scale studies are needed, the presence of anti-erythrocyte antibodies and signs of erythroid regeneration may suggest a possible immune-mediated hemolysis that can induce anemia in dogs with IRE, together with the chronic inflammation.