Dynamic mobility of immunological cells expressing S100A8 and S100A9 in vivo: a variety of functional roles of the two proteins as regulators in acute inflammatory reaction.

The immunological properties of rat S100A8 (r-S100A8) and S100A9 (r-S100A9) in immune cells are poorly understood. Enzyme-linked immunosorbent assay (ELISA) for r-S100A9 enabled us to discuss the differential functional roles of the two proteins, and their localization in the cells was observed microscopically. Recombinant human S100A8 (rh-S100A8) or S100A9 (rh-S100A9) were intravenously administrated into rats with LPS-induced liver damage. ELISA was used to measure the serum concentration of S100A9 in the rats. Western blotting and a preparative ELISA were used to prove specificity and avidity of monoclonal antibodies for r-S100A8 and r-S100A9. Immunohistochemical staining was carried out to visualize intracellular localization of the two proteins in the immune cells using the antibodies. When rh-S100A8 was intravenously injected in the rats (B group), the serum concentration of r-S100A9 apparently decreased as compared with that of the positive control rats (A group). The activities of AST, ALT, and LD in the rat sera (B group) also significantly went down in comparison with those of the rats (A group). Although both the S100A8 and S100A9 were abundantly expressed in activated immune cells, quite difference of not only their intracellular localization but also distribution of the cells expressing the two proteins was microscopically observed. In the rats (B group), less number of the immune cells or less amount of r-S100A8 and r-S100A9 in the cells than those of the rats (A group) was also seen. The r-S100A8 could serve as a regulator of acute inflammatory reaction in the rats with LPS-induced damage.