Immune Function in Critically Ill Dogs.

Background: People with critical illness (CI) commonly develop various forms of immune dysfunction, however, there is limited information concerning immune dysfunction in dogs with CI.

Hypothesis: The immune response in CI dogs differs from that of healthy dogs.

Animals: Immunologic variables were compared between 14 dogs with CI, defined as APPLE score of >20 points, admitted to the University of Missouri Veterinary Health Center Small Animal Clinic Intensive Care Unit and healthy controls (n = 15).

Methods: Cohort study evaluating constitutive and lipopolysaccharide (LPS)-stimulated TNF-α, IL-6, and IL-10 production, phagocytosis of opsonized E. coli and respiratory burst capacity after opsonized E. coli or phorbol 12-myristate 13-acetate (PMA) stimulation, peripheral blood lymphocyte phenotype, and monocyte expressions of HLA-DR and TLR-4.

Results: Lipopolysaccharide-stimulated leukocyte TNF-α (median, Q1, Q3; CI, 49, 49, 120; control, 655, 446, 1174 pg/mL; P = < 0.001), IL-6 (median, Q1, Q3; CI, 49, 49, 64; control, 100, 49, 166 pg/mL; P = 0.029), and IL-10 (CI, 49, 49, 56; control, 96, 49, 203 pg/mL; P = 0.014) production and both E. coli (median, Q1, Q3; CI, 60.5, 43, 88.5; control, 86.6, 81, 89.2%; P = 0.047) and PMA (CI, 40, 11.7, 70; control, 93, 83, 97.6%; P = < 0.001)-stimulated respiratory burst capacity significantly decreased in CI dogs. Percentage of monocytes expressing TLR-4 greater in the CI dogs (median, Q1, Q3; CI, 46.9, 24.3, 64.2; control, 16.4, 9.4, 26.2%; P = 0.005).

Conclusion: These findings suggest dogs with CI develop immune system alterations that result in reduced respiratory burst function and cytokine production despite upregulation of TLR-4.