Immunodiagnostic assays

The immune system is a complex interactive network. Defects in its function can be characterized broadly as being the result of actual deficiencies in the network or misdirection of normal immunologic functions. The assays that are available to detect deficiencies in the immunologic network barely scrape the surface of the possibilities. These assays primarily evaluate humoral immune function, but undetected defects in innate and cellular immunity are sure to exist. Although assays of humoral immunity have allowed the characterization of a number of immunodeficiency syndromes in horses, closer evaluation of the equine immune system using newer assays described in this text, as well as future assays yet to be developed are sure to determine new syndromes. Assays of misdirected immunologic functions have been limited to detection of misdirected antibody responses, but the dependence of antibody production on help from T cells could reflect an underlying defect of cellular immunity. Similar to immunodeficiency syndromes, misdirected responses of the innate and adaptive arms of immunity are sure to occur but will only be detected by more diligent surveillance of diseased horses and application of new immunodiagnostic technologies.