While information is available on the immune system of terrestrial mammals, very little is known about the immune system of marine mammals, especially the total aquatic cetaceans. The increased incidence of mass mortalities, strandings, disease outbreaks, and a threatened environment, in addition to health maintenance of cetaceans placed under human care, makes it imperative that we learn about their immune system.

Lymphoid organs were collected from white whales, Delphinapterus leucas, ranging in age from less than one to 16 years to investigate overall morphology and innervation at the light and electron microscopic levels. Morphology of white whale lymphoid organs was similar to that of other mammalian lymphoid organs with a few differences. Catecholamine histofluorescence and tyrosine hydroxylase (the rate-limiting enzyme in norepinephrine synthesis) revealed the presence of nerve fibers in parenchymal compartments of lymphoid organs, closely associated with cells of the immune system. This anatomical link between the nervous and immune systems provides a pathway for external stimuli, such as stress to affect immunocompetence.

Studies on peripheral blood lymphocytes reveal a high percentage of class II-positive cells and a population of approximately 10-15% immunoglobulin-positive cells. Molecular techniques and classical monoclonal antibody production are currently being utilized in our laboratory to generate reagents to identify lymphocyte subsets in tissues as well as peripheral blood in cetaceans. These reagents will not only increase our knowledge of the cetacean immune system, but will aid in the health care and rehabilitation of stranded and/or sick cetaceans.