Alcohol and the immune system

Alcohol Health & Research World, Wntr, 1992 by Gary A. Roselle

Researchers also have examined effects of alcohol on the histology of lymphoid organs (the thymus and spleen) in laboratory animals. Alcohol intake has been shown to decrease thymic weight and reduce the number of cells found in the thymus. This effect was accompanied by a decrease in responsiveness of thymocytes to mitogen stimulation, indicating an impairment in these cells' capacity to undergo the proliferation and differentiation integral to effective T-cell responses (Jerrells et al. 1986; Grossman et al. 1988; Jerrells et al. 1989; Chang et al. 1990; Jerrells et al. 1990b). Studies of the spleen have demonstrated similar reductions in cell numbers and decreased mitogen responses following alcohol administration, with similar implications for resistance to disease (Jerrells et al. 1988).

Saad and Jerrells (1991) have published a detailed investigation of alcohol's effects on lymphocyte populations and lymphoid organs in mice. Following 2 weeks of alcohol ingestion, cell numbers in the spleens and thymuses of these animals were found to be reduced. Within the spleen, B-cell numbers were most significantly reduced, but the overall structure of the spleen remained intact. Within the thymus, there was a greater reduction in numbers of immature thymocytes(2) than in mature thymocytes, indicating a rather specific effect of alcohol. Further, structural abnormalities could be observed in thymuses taken from alcohol-fed animals: in stained tissue sections, the thymic cortex (the outer layer of the thymus, consisting largely of immature thymocytes) was not identifiable after 2 weeks of alcohol ingestion. These findings suggest that alcohol may influence the migration of thymocytes within the thymus, and as a result, may alter normal patterns of T-cell development and migration from the thymus to peripheral blood and lymphoid tissues.

Further documentation of abnormalities in thymocyte characteristics (and in a variety of other immunologic parameters) are found in studies of fetal alcohol syndrome (Ewald 1989; Ewald and Walden, 1988). (These abnormalities are discussed in greater detail in the article by Giberson and Weinberg, pp. 29-38.)

EFFECTS ON ANTIBODY PRODUCTION

Even though alcoholics demonstrate normal numbers of circulating B-cells (Roselle et al. 1988), they frequently demonstrate elevated levels of serum antibodies, or immunoglobulins (Ig), particularly those of the IgG and IgA classes (Nouri-Aria et al. 1986). Elevated serum antibody levels may be related to liver disease and may indicate impaired regulation of B-cell function (Nouri-Aria et al. 1986).

Experiments that have attempted to explain these abnormalities have found that alcohol can have both direct and indirect effects on antibody-producing B-cells. However, for the most part these experiments have demonstrated that alcohol inhibits B-cell production of antibody, results that are difficult to reconcile with clinical findings.

In vitro experiments have demonstrated that physiologic doses of alcohol can suppress antibody production through direct effects on B-cells (Aldo-Benson et al. 1986; Aldo-Benson 1989a,b). The biochemical mechanisms involved in this inhibition are unclear, since, in these studies, alcohol had no apparent effect on those membrane and intracellular changes that normally occur when B-cells are stimulated to produce antibody.