Expression of Major Histocompatibility Complex class I and II in a case of Neospora caninum myositis in a dog.

Neosporosis was diagnosed in a 2-month-old dog by indirect immunofluorescence antibody test (IFAT) and confirmed by means of histopathology and immunohistochemistry. The associated myositis was characterized by Major Histocompatibility Complex expression on some muscle fibres. This finding indicates an immunological activation, of the muscle cells that, acquiring Major Histocompatibility Complex expression, may, in some way, contribute to antigen presentation. A possible role of these glycoproteins in the pathogenesis of Neospora-associated myositis is discussed.