Leukocyte subset analysis

A subset of nanoparticles were tested in mice (28e). Nanoparticles with similar activity profiles in vitro exerted similar effects on monocyte numbers in vivo. Alterations of leukocyte subsets, including an increased monocyte fraction, can be a sign of proinflammatory or other toxic exposure. Second, monocytes are phagocytic and take up certain nanoparticles more than other cell types. Finally, nanomaterials have been shown to cause pleiotropic effects on immune cells that are very sensitive to the materials composition and surface. Because this analysis compares biologic activity across nanoparticles, we can stiU draw conclusions as to similarities and differences among nanoparticles based on this in vitro data. The authors emphasis on comparing across nanomaterials becomes progressively more useful as the number of well-characterized nanomaterials increases (28e). 

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. 

Willard-Gallo, K.E., 1984, Analysis of normal subset-specific and disease-specific human leukocyte proteins by cell sorting and two-dimensional electrophoresis. Ann. N. Y. Acad. Sci. 428 201-222. 

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