Organ function biomarkers

Functional Functional biomarkers can be used to assess if the organ or the tis-... 

Pb exposure at relevant levels does not produce overt cytotoxicity of immuno-cytes. Instead, immune-associated health effects result from dysregulation and shifts in functional capacity rather than profound lymphoid deficiencies. As a result, the most sensitive biomarkers and indicators of Pb-induced immunotoxicity are those associated with specific functional capacities as opposed to more classical measures of cell enumeration and/or lymphoid organ pathology. 

The various organs of the immune system such as spleen, lymph nodes, thymus and bone marrow containing the cells involved in the various immune responses offer the possibility to harvest these cells and perform in vitro assays for evaluation of effects on the immune system. When part of an in vivo animal study this may indicate a direct toxic effect of pharmaceuticals, that is, immunosuppression (Table 18.2). So, it is feasible to obtain cell suspensions for further evaluation such as determination of cellular subsets of T and B leukocytes by fluorescent activated cell sorter analysis (FACS analysis), and determination of natural killer (NK) cell activity of the spleen cell population. An advantage of this approach is that it may lead to identification of a biomarker to be used in clinical studies. In addition, in vitro stimulation of spleen cells with mitogens activating specific subsets may indicate potential effects on the functionality of splenic cell populations. Concanavalin A (Con A) and phytohemagglutinin (PHA) activate Tcells, while lipopolysaccharide (LPS) activates primarily B cell populations. Blood is collected for total white blood cell (WBC) determination and blood cell differential count. In addition, serum can be obtained for determination of serum immunoglobulins. 

The committee recommends that investigators, including CDC, that conduct surveys of biomarkers in the population should routinely collect detailed information about SES, lifestyle, and other cofactors on each subject and routinely present results organized so as to address the question of whether biomarker concentrations vary as a function of each. Epidemiologic analyses of biomarkers in relation to health should routinely include appropriate adjustments for such covariates. 

Knowing some potential target organs and systems affected by various tin compounds, it may be possible to develop biomarkers specific to effects. Examples include immunological and neurobehavioral tests as compound-specific pulmonary, liver, and kidney function studies. The primary objective of such biomarkers would be to predict adverse health effects in exposed individuals and populations. 

The preservation of organic matter in coastal and estuarine sediments is believed to be principally controlled by productivity, sedimentation accumulation rate, bottom water and sediment redox conditions, and sorption as a function of specific surface area of sediments (see review, Hedges and Keil, 1995). In this section the focus will be primarily on factors controlling preservation or organic matter in estuarine sediments the use of chemical biomarkers for historical paleo-reconstruction of past estuarine environments is discussed in chapter 15. 

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