Macrophage assessment

What is less clear, at present, is the role that other traditional immune evaluations may play in DIT assessment, including cytokine evaluation, flow cytometry, and immunomics. Based on the literature to date and the specific protocols employed, cell population changes, cytokine production alterations, dendritic cell and/or macrophage assessment, and immune histologic manifestation seem to be accessory parameters that are supportive of functional changes but not of themselves sentinel predictors of DIT. As described for adult animals (see Chapter 4), cytokine measurements in serum or peripheral blood may potentially be performed as a functional means to assess... 

Follow-on studies are also recommended as needed. These include determination of potential test article effects on blood or tissue immunophenotypes (by flow cytometry or immunohistochemistry), natural killer cell, macrophage, or neutrophil function, host resistance to infection or tumors, and cell-mediated immunity. The important issue in all of these guidelines is this do not ignore signs of immunotoxicity, and assess these findings when observed. 

COUPLING FLOW CYTOMETRY WITH IMAGE ANALYSIS-ASSESSING THE ROLE OF MACROPHAGES IN TISSUE INJURY... 

In summary, flow cytometry is clearly useful in evaluating macrophages and their role in toxicity. A major advantage of this technology is the rapid and accurate identification of subpopulations of responding cells from within a mixed population. There is no doubt that the utility of flow cytometry will increase in the future as new fluorescence probes are developed that allow investigators to more clearly assess various macrophage characteristics and the response of these cells to xenobiotics. 

In contrast to adaptive immune function, fewer studies have examined effects of TCDD on the innate immune system. Furthermore, of the limited data available, much of it is inconsistent. For example, natural killer (NK) cell activity has been reported to be unaffected,80,93 diminished,94 and increased95 following exposure to TCDD. Although a thorough assessment of AhR expression in all innate cell lineages has not been conducted, neutrophils and macrophages express the AhR,8,96 and neutrophils are affected... 

Effects of TCDD on macrophages have also been examined. When assessed ex vivo, macrophage functions such as tumor cell lysis, phagocytosis and oxidative burst were not suppressed by exposure to TCDD.9396 101 In other experimental systems, exposure to TCDD increases IL-1 and TNF production by macrophages.99 102 103 However, the ability of TCDD to alter IL-1 and TNF production is likely organ- or stimulus-specific, because in the context of respiratory viral infection, exposure to TCDD had no effect on IL-1 or TNF-a levels.80... 

As described previously, the humoral immune response results in the proliferation, activation, and subsequent production of antibodies by B cells following antigenic exposure and stimulation. The functionality and interplay between the three primary types of immune cells (macrophage, B cells, and T cells) required to elicit a humoral response can be assessed through various in vitro assays using cells from the peripheral blood or lymphoid tissues. 

Type IV hypersensitivity responses are elicited by T lymphocytes and are controlled by accessory cells and suppressor T cells. Macrophages are also involved in that they secrete several monokines, which results in proliferation and differentiation of T cells. Thus, there are numerous points along this intricate pathway in which drugs may modulate the final response. To achieve a Type IV response, an initial high-dose exposure or repeated lower-dose exposures are applied to the skin the antigen is carried from the skin by Langerhans cells and presented to cells in the thymus to initiate T-cell proliferation and sensitization. Once sensitized, a second challenge dose will elicit an inflammatory response. Thus, before sensitivity can be assessed, each of the models used to evaluate dermal hypersensitivity requires as a minimum ... 

Wiley JS, Cebon JS, Jamieson GP, Szer J, Gibson J, et al. 1994. Assessment of proliferative responses to granulocyte-macrophage colony-stimulating factor (GM-CSF) in acute myeloid leukaemia using a fluorescent ligand for the nucleoside transporter. Leukemia 8 181-185. 

The presence of protein-hydropic degeneration (Fig. 13a), punctuate infiltration and necrosis, reaction of hepatic macrophages (Fig. 13b), nuclear polimorphysm (Fig. 13c), inflammatory infiltration of portal tracts and perivenular infiltration (Fig. 13d) were considered in the assessment of morphological alterations in the liver of the mice. 

Pessina, A., Croera, C., Bayo, M., Malerba, L, Passardi, L, Cavicchini, L., Neri, M.G. and Gribaldo, L. (2004) A methylcellulose microculture assay for the in vitro assessment of drug toxicity on granulocyte/macrophage progenitors (CFU-GM). Alternatives to Laboratory Animals, 32, 17-23. 

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