Enhanced Production of IL-10 in PCR-Positive Dogs Infected with E. canis and A. phagocytophilum Facilitate Specific Immune Responses

Infection of dogs with the tick-borne rickettsiae <i>Ehrlichia</i> and <i>Anaplasma</i> provokes an immune response mediating the pathology and bacterial resistance. IL-10 is the main anti-inflammatory cytokine and plays a multifaceted role in host protection. The study aimed to investigate circulating IL-10 in 32 dogs naturally infected with <i>A. phagocytophilum</i> and <i>E. canis</i>, identified by PCR positivity, and 33 PCR-negative animals which tested positive for antibodies against these pathogens, as well as 22 healthy animals. The highest quantity of IL-10, measured by ELISA, was observed among dogs positive simultaneously for anti-<i>E. canis</i> and anti-A. <i>phagocytophilum</i> IgG antibodies, followed by dogs positive for anti-<i>E. canis</i> only. The concentration of IL-10 in PCR-positive dogs was almost three and a half times higher than that measured in the control group (77.09 ± 23.61 pg./mL vs. 21.55 ± 4.61 pg./mL; <i>p</i> = 0.0015) and five times higher than the concentration of interleukin in PCR-negative animals (77.09 ± 23.61 pg./mL vs. 14.86 ± 3.01 pg./mL; <i>p</i> = 0.000016). The highest level of IL-10 was observed in PCR-positive dogs with mixed infection (120.54 ± 44.18), followed by the level in PCR-positive dogs for <i>E. canis</i> only (78.81 ± 16.92). The lowest level of IL-10 was observed in PCR-positive dogs for <i>A. phagocytophilum</i> only (56.32 ± 12.68). We may suggest that infection with <i>E. canis</i> and <i>A. phagocytophilum</i> stimulates the IL-10 production in dogs, which may facilitate specific antibody responses.