when facilities and expertise are limited. Each of these scenarios independently can prohibit the traditional use of density gradient-separated (Bøyum, 1977) peripheral blood mononuclear cells (PBMC) for measurement of T-lymphocyte functions in vitro. Preparation of a PBMC suspension requires an abundance of blood and well-trained laboratory workers, and it is time consuming. In an effort to demonstrate various effects on the cellular immune system of humans, several investigators have established the use of whole-blood cultures for measurement in vitro of lymphocyte proliferation (Bloemena et al., 1989; Bocchieri et al., 1995; Fletcher et al., 1992; Fritze and Dystant, 1984; Kramer and Burri, 1997; Kramer et al., 1997, in press; Leroux et al., 1985; Zhang et al., 1995) and interleukin production (DeForge and Remick, 1991; DeGroote et al., 1992; Desch et al., 1989; Ellaurie et al., 1991; Elsässer-Beile et al., 1993; Kirchner et al., 1982; Lyte, 1987; Nerad et al., 1992; Oliver et al., 1993). The use of whole-blood cultures offers four advantages: (1) only small amounts of blood are required; (2) many samples can be processed at once; (3) samples contain their own natural milieu of blood components, both cellular and humoral (fluid components of blood); and (4) whole-blood cultures are more cost effective than are cultures containing PBMC.

Using whole-blood cultures has helped to establish associations between suppressed mitogenic proliferative responsiveness of T-lymphocytes in vitro and each of the following: marathon running (Eskola et al., 1978), intense treadmill exercise (Nieman et al., 1994), intense military training with reduced caloric intake (Kramer et al., 1997b), certain types of cancer (Fritze and Dystant, 1984), infection with human immunodeficiency virus (Bocchieri et al., 1995; Kramer and Chan, 1994), marginal zinc status (Kramer et al., 1990), and a diet low in carotene (Kramer and Burri, 1997). Whole-blood cultures have also been used to demonstrate the suppressive effects of treatment with oral corticosteroids on production of interferon-gamma (INF-γ) in response to dust mite antigen in vitro (Ellaurie et al., 1991), and to monitor the effects of biologic response modifiers on interleukin production by immune cells (Elsässer-Beile et al., 1993).

Healthy adults donated blood for this series of experiments. Study of the donors was approved by the Institutional Review Board of Johns Hopkins University and by the U.S. Department of Agriculture Human Studies Review Committee. The project was conducted in accord with the Helsinki Declaration of 1975 as revised in 1983.