Isotype-specific antibodies in horses and dogs with immune-mediated hemolytic anemia.

This research investigates the classes of antibodies found in horses and dogs suffering from a condition called immune-mediated hemolytic anemia (IMHA) using a technique known as direct immunofluorescence (DIF) flow cytometry. The results demonstrated that DIF flow cytometry was more sensitive in identifying IMHA in dogs, while the Coombs’ test, another diagnostic tool, showed better specificity. Importally, the DIF method was efficient in monitoring therapy response in a horse case with neonatal isoerythrolysis.

Study Methods and Participants

• The study assessed sample groups of three horses and twelve dogs diagnosed with immune-mediated hemolytic anemia (IMHA), a condition where the immune system destroys its own red blood cells.
• Control samples from 12 clinically healthy horses and dogs were also tested for comparison and to determine levels of non-disease related antibody binding.

Direct Immunofluorescence Flow Cytometry

• The research used direct immunofluorescence (DIF) flow cytometry to identify the classes of antibodies bound to erythrocytes (red blood cells).
• There was non-specific binding observed when a specific agent, fluorescein isothiocyanate-conjugated goat anti-equine immunoglobulin G, was used. This interference could be removed by using the F(ab’)2 fragment of the same antibody type. For other class-specific antibodies used in this study, no significant background binding was observed.

Comparison of Diagnostic Techniques

• The results obtained from the DIF method were compared with those of the Coombs’ test, another method used to diagnose autoimmune hemolytic anemia.
• The DIF method was found to be more sensitive than the Coombs’ test in diagnosing IMHA in dogs (100% vs 58%).
• However, the Coombs’ test outperformed the DIF method in terms of specificity (100% vs 87.5%).
• With reference to clinical parameters and response to treatment, both the positive and negative predictive values were higher for the DIF test (92% and 100%) than for the Coombs’ test (100% and 62%).
• The DIF assay could detect low levels of cells bound with antibody in 5 dogs that tested negative in the Coombs’ test.

Antibody Detection in Animals

• In dogs, the DIF test detected both IgG and IgM antibodies on red blood cells. Five dogs had both types of antibodies present, 5 had only IgG, and 2 had only IgM.
• In horses, the DIF method was found effective in monitoring the therapeutic response in a foal suffering from neonatal isoerythrolysis, a hemolytic disease of the newborn. It also identified surface-bound IgG antibodies in three horses, one of which was suspected to have penicillin-induced IMHA, another was the aforementioned foal diagnosed with neonatal isoerythrolysis, and the third was a foal with a bacterial infection (clostridial septicemia).