Murine CD5⁺, CD8⁺ Normal Fetal Liver Cells Enhance an Immune Response: Benzo(α) Pyrene-Exposed CD5⁺ Fetal Liver Cells are Inhibitors

Abstract

The effects of 150 ug benzo(α)pyrene/gm body weight given intraperitoneally to the pregnant mouse at mid-gestation leads to long-lasting (> 18 months post-birth) immune deficiency in the progeny. Although the progeny are immunodeficient their T cell subsets induced marked enhancement and/or inhibition of cell proliferation in an immune response. Earlier we saw a striking increase (up to 7-fold) in CD8⁺ cells in the 18 day gestation liver of benzo(α)pyrene-exposed fetuses. We hypothesized that immune deficiency in carcinogen-exposed progeny could be attributed to an increase in classical CD8⁺ suppressor T-cells. Surprisingly, however, we found that CD8⁺ and CD5⁺ (Lyt 1⁺) cells of normal fetal liver enhance cell proliferation in an immune response. However, liver CD5⁺ cells from benzo(α)pyrene-exposed fetuses led to a dramatic reduction of the enhancing effect. Thus, as a novel finding, it appears that the profile of CD5⁺ cells, under the ontogenic influence of benzo(α)pyrene, transforms from cells that normally augment cell proliferation in an immune response to cells that are inhibitors. On the other hand the functional status of CD8⁺ cells is not affected. This change in physiological status of CD5⁺ cells may have important implications on T and B cell interactions, and the role of CD5⁺cells in T cell receptor signaling.

Keywords:

• CD8⁺
• CD5⁺
• Fetal Liver
• Immune Response

ACKNOWLEDGMENTS

Supported by grant #R815813 from the United States Environmental Protection Agency, and grant # PCE–5053–G–00–3062 from the United States Agency for International Development. Assistance from Dr. Joy Zhu, Morehouse School of Medicine, is recognized for contribution in flow cytometry, and thanks to Ms. Nicole Downing for editorial assistance.