Common canine autoimmune disorders (Proceedings)

There are over 10 textbooks of veterinary physiology published since 2005 and currently in use in schools throughout Europe and North America and there are probably a similar number used in Asia and South America. Indeed, physiology is the breathe of medicine and is as much a requirement in the curricula of medical schools in 2008 as it was in 1908. All these texts include chapters on the circulatory, respiratory, and nervous systems, along with the latest advances in cell biology, yet there is not a single chapter on the immune system in any of them, with the possible exception of descriptions of the lymphatic organs. Quite strikingly, if one reviews any of the several dozens of textbooks of medicine, whether in family practice, surgery, orthopedics, or internal medicine, the term "immunology" is found throughout multiple areas of these specialties. This statement takes on added significance based on the growing realization that autoimmunity in the canine is considerable more common than once believed.

The history of immunology as a discipline per se can be traced back to the spectrum of infectious diseases and allergy. It was not until later that the conceptual revolution began in defining the nature of tolerance and the distinction between self and non-self thanks to the Nobel laureate Paul Ehrlich. Ehrlich became famous not so much for his contributions in autoimmunity, but rather because he coined "The Horror Autotoxicus" stating that an immune response against one's own body elements would necessarily lead to death; the concept of autoimmunity can be traced back to these years. Following the 1947 discovery of LE cells and later of serum antinuclear antibodies (ANA), it became clear that there are not only multiple autoimmune diseases, but also that autoantibodies are more numerous than autoimmune diseases. Our knowledge on autoimmunity has paralleled the fast pace of discovery for new diagnostic tools and we are currently in the era of microarrays to diagnose and ideally predict autoimmunity.

For several decades now autoimmune diseases, were often lumped under the vague term of 'collagen vascular pathology'. In earlier years, autoimmune diseases were considered rare and the appearance of autoantibodies was often considered pathognomonic until the dissection of serum ANA drastically changed the scenario. The increased serological sophistication demonstrated that autoantibodies were detected also in a fraction of otherwise normal dogs without developing clinically overt autoimmunity during follow-up and in some cases autoreactivities occurred naturally. In this latter case, autoantibodies may further provide new links to unsuspected comorbidition. Similarly, it became clear that ANA subtypes provided clues not only to clinical correlations but also to the etiology of autoimmunity.

Autoimmune diseases are believed to cumulatively affect 1-3% of the general canine population and are a significant cause of morbidity and mortality worldwide. Indeed we recognize in dogs systemic lupus erythematosus, rheumatoid arthritis, autoimmune anemia/thrombocytopenia, myasthenia gravis and several dermatologic diseases to name just a few.

The classification of a clinical condition as autoimmune poses several dilemmas. In this talk I will emphasize the following:

1. What is autoimmunity?

2. How is autoimmunity diagnosed?

3. What are the most frequent autoimmune diseases of dogs?

4. Is autoimmunity in the canine increasing in incidence?

5. What is the future of diagnostic tools?

References

1. I.R. Mackay, The etiopathogenesis of autoimmunity, Semin Liver Dis 25 (2005), pp. 239–250.

2. P.I. Martin, A.I. Malizia and E. Rewald, A propos time and autoimmunity, Clin Rev Allergy Immunol 34 (2008), pp. 380–384.

3. E. Tonutti, D. Visentini and N. Bizzaro, Interpretative comments on autoantibody tests, Autoimmun Rev 6 (2007), pp. 341–346