For instance, IL-1 generated by antigen-presenting cells affects the temperature regulatory centre (induction of fever) and the sleep regulatory centre (induction of slow-wave sleep) in the hypothalamus (Dinarello, 1992).
In humans, conditions of acute psychological stress include bereavement (Bartrop et al., 1977), marital disruption (Kiecolt-Glaser et al., 1987), and examination periods (Kiecolt-Glaser et al., 1986), and these can be associated with a decrease in immune status (Kiecolt-Glaser & Glaser, 1986) which can result in increased risk for infection, including common respiratory tract infections, e.g.
Time course for recovery from adverse immunological effects a Measures of specific and nonspecific cell-mediated immune responses that also may be considered useful in an immunotoxicity screen 3.2.4 United States Food and Drug Administration, Center for Food Safety and Applied Nutrition panel The United States Food and Drug Administration is considering testing guidelines for evaluating the immunotoxic potential of direct food additives (Hinton, 1992).
3.2.3 United States Environmental Protection Agency, Office of Pesticides panel The United States Environmental Protection Agency has proposed a tiered approach to the evaluation of biochemical pest control agents, which fall under the subdivision M guidelines for pesticides (Sjoblad, 1988).
The assays that make up the NTP tier approach have undergone various revisions, partly on the basis of an immunotoxicological review of compounds evaluated in this tier structure (Luster et al., 1992).
The intravenous route is that preferred for sensitization; intraperitoneal injections can be used but significantly increase the potential for nonresponding animals as a result of a poor injection.
Serial dilutions are injected into the skin of rats, sensitizing local mast cells; the specific antigen is then injected intravenously, simultaneously with Evans blue.
The cells have enhanced cytolytic function after activation with a variety of stimuli, including viral infection (Stein-Streinlein et al., 1983), BCG (Tracey et al., 1977), IL-2 (Henney et al., 1981; Domzig et al., 1983; Lanier et al., 1985; Malkovsky et al., 1987), interferon, and interferon inducers (polyI:C) (Tracey et al., 1977; Oehler & Herberman, 1978; Djeu et al., 1979a,b).
While both the nonspecific and immune-mediated phagocytosis assays are useful for understanding the potential mechanisms of action of compounds, changes in phagocytic activity in these in-vitro assays have not been found to be predictive of immunotoxicity.
Animals are sacrificed on day 4 after injection, and spleen cells are prepared by mincing the spleen between two frosted microscope slides, teasing it apart with forceps, or passing it through a small mesh screen; all of these methods are satisfactory, and that used to prepare single splenocyte cultures varies from laboratory to laboratory.
The plates are then washed to remove unbound erythrocytes; an ammonium chloride solution is added to lyse adhered erythrocytes, and the supernatant is collected and counted to determine adherence of the erythrocytes to the macrophages.
Some of the activation markers that have been studied are F4/80 (Austyn & Gordon, 1981), Mac-1 (Springer et al., 1979), Mac-2 (Ho & Springer, 1984), transferrin receptor (Neckers & Cossman, 1983), and IL-2 receptor (Cantrell et al., 1988).
A plaque results from the lysis of sheep erythrocytes and is elicited as a result of the interaction of complement and antibodies directed against sheep erythrocytes, which are produced in response to the intravenous sensitization.
The markers that have been routinely used in studies of immunotoxicity conducted for the NTP in mice and the cell types they identify are shown in Table 11.
While many of the markers have been used in immunological investigations, very few have been evaluated with a large number of immunosuppressive compounds.