Effect of polycyclic aromatic hydrocarbons on immune responses in fish: Change in melanomacrophage centers in flounder ( Pseudopleuronectes americanus) exposed to hydrocarbon-contaminated sediments

There is presently considerable debate on whether the concentrations of xenobiotics commonly found in the environment are high enough to affect immune functions in humans or other animal populations. Only a limited number of immunotoxicity studies have been carried out with fish. 1–3 Melanomacrophage centers (MMC) represent the primitive analogs of lymph nodes in mammals and are believed to be an integral component of the cellular immune system in fish. 4 We investigated the potential for change in MMC in a long-term study with winter flounder exposed to sediments contaminated with a petroleum source of polycyclic aromatic hydrocarbons (PAH). Numbers of MMC were reduced in liver tissues of fish exposed to total PAH concentrations in the 25–50 μg/g (ppm) range and higher. Results support the hypothesis that PAH concentrations in heavily polluted harbors (and similar) may be sufficiently high to affect immune responses in fish.