Flow Cytometric and Immunohistochemical Evaluation of Ethanol‐Induced Changes in Splenic and Thymic Lymphoid Cell Populations

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Abstract
Ethanol‐induced alterations in the immune system are thought to play a major role in increasing the susceptibility of alcoholics to infections and tumors. One important change in the immune system is the noted loss of lymphoid cells from the thymus and spleen. To examine these alterations we used a model system where C57B1/6 mice were pair‐fed either a Leiber‐DeCarli diet containing 7% (v/v) ethanol or an isocaloric control diet. Mice receiving ETOH for 7 days showed a loss of cells from the spleen and thymus; this loss was even more severe after withdrawal for 1 day. The most profound changes were seen after 2 weeks of ETOH. Spleen and thymus cell numbers were reduced to 36% and 6.2%, respectively compared to control mice. Staining of thymocytes with monoclonal antibodies to lymphocyte surface markers and evaluation with flow cytometry revealed that immature thymocytes (PNA+, CD4+/CD8+) were most reduced. Mature thymocytes (CD4+/CD8‐ or CD4‐/CD8+) were depleted, and the CD4+ to CD8+ ratio was increased. Sections of thymus stained with hematoxylin and eosin or with immunohistochemical methods showed atrophy and lymphoid cell depletion. No cortex was histologically identifiable after 2 weeks of ETOH. The spleen cells most affected by ETOH were the B cells. They were reduced to 8.2 × 106 cells/spleen (31.5% of the lymphocytes), as compared to 38.5 × 106 cells/spleen (50.3% of the lymphocytes) in the control mice. The spleen was atrophic, but the immunoarchitecture was preserved. Ethanol causes a depletion of lymphocytes from the spleen and thymus with alterations in lymphocyte subpopulations. Immature cells in the thymus are most susceptible, and the changes are more severe with longer periods of consumption.