Abstract

Basic function and defense mechanisms of the immune system of cetaceans, total aquatic mammals, are not well characterized and understood like the immune system of terrestrial mammals. Mass die-offs, disease, environmental pollutants, and healthcare of cetaceans kept under human care, require a better understanding of this defense system in cetaceans. Our laboratory has carried out in-depth studies on the morphology and innervation of organs of the cetacean immune system at the fight and electron microscopic levels, as well as descriptive and functional lymphocyte studies, stressing the value of cetacean-specific reagents to continue investigation of the immune system.

To this end, we have cloned beluga CD4 (a cell surface protein on T helper lymphocytes), by screening a beluga whale cDNA thymic library, with a beluga-specific CD4 probe. The fun length transcript of beluga CD4 consists of 455 amino acids, sharing 60% identity to the human protein sequence, and 50% identity to the mouse CD4 sequence. Another CD4 clone was analyzed, which when lined up with the human sequence, lacked the transmembrane domain, resembling a soluble form of CD4 (sCD4).

Peptides were designed and synthesized to either full length beluga CD4, sCD4, or to a region common to both CD4 transcripts, and injected into rabbits for antibody production. These antibodies will be used to label CD4-positive lymphocytes and sCD4 in organs of the immune system, and peripheral blood lymphocytes of healthy, sick or stranded cetaceans.