Contaminant-induced immune alterations in the Pacific harbor seal, Phoca vitulina richardsi, of the central coast and San Francisco Estuary

Recent observations pertaining to the increasingly frequent and severe die-offs of marine mammals inhabiting polluted waters suggest the possibility of an important contributing role of contaminant-induced immune suppression. California's San Francisco Estuary (SFE) and central coast include many highly contaminated environments; water, sediments and tissues of aquatic organisms contain high levels of persistent organic contaminants. The proposed research explores the potential immunomodulatory role of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), two ubiquitous marine pollutants of this region, in the harbor seal, a high trophic level integrator of environmental contamination of coastal marine food webs. Specifically, this project aims to (1) assess the immune competence of free-ranging harbor seals of the SFE and central coast via in vitro assays of immune function using peripheral blood mononuclear cells (PBMC); (2) determine environmental exposures to selected PAHs and PCBs in these same animals; (3) assess immune alterations of seal lymphocytes (PBMC from captive harbor seals with minimal previous exposure to PAHs and PCBs) exposed in vitro to a model PAH or PCB; and (4) test the hypothesis that observed effects are dependent on the aryl hydrocarbon receptor (AhR)-cytochrome P450 (P450) pathway. Effects of contaminant exposure on cellular immunity will be indicated by in vitro assays of lymphocyte function including capacity of lymphocytes to proliferate after stimulation, programmed cell death (apoptosis), and expression of protein tyrosine kinase genes. This study will significantly contribute to an improved understanding of the role of environmental contaminants in compromising health of marine mammals. Such information may lead to improved management strategies to reduce future impacts