Results
In order to obtain information on the inflammatory potential of LL particles and the impact of the calcium InsP 6component on this potential, we injected i.p. LL particles containing calcium InsP 6 (wpLL) or freed from this component (pLL). Injection of the LL materials at the dose under study brought about only a trend towards higher total numbers of cells in the cavity, but did cause significant influxes of eosinophils, neutrophils and monocytes (Fig. 1a - d). An increase in the number of SPM/DC was also observed, which reached significance for pLL but was only a trend for wpLL (Fig. 1 e). In all likelihood, this increase was mostly accounted for by SPM, which on the basis of previous studies of macrophage recruitment to the body cavities (20–22, 26, 31) likely arose from recruited monocytes. We also detected significant increases in MHCII- F4/80med macrophages (Fig. 1 f). These cells are deduced to derive from SPM on the basis of previous studies on inflammatory stimuli injected into the peritoneal cavity (26). In agreement, this population did not express the long-term resident macrophage marker Tim4 whereas approximately 4/5 of the major resident macrophage population (the F4/80hi LPM) expressed this marker as expected (data not shown) (32). LPM numbers decreased sharply in response to LL materials (Fig. 1 g), as expected when an inflammatory stimulus is injected into the peritoneal cavity (22, 33, 34). Notably, the presence of the calcium InsP 6 component did not enhance cell recruitment nor disappearance of LPM, and it actually generated trends towards weaker recruitment of all the inflammatory cell types studied (Fig. 1 a – f).
We next tested the contribution of the mucin glycans to the inflammatory cell recruitment and disappearance of resident macrophages observed. For this purpose, we injected pLL, which was untreated, treated with periodate to destroy the terminal monosaccharides (pLL periodate), or subjected to a mock treatment (pLL mock). In comparison to mock-treated particles, periodate-treated particles tended to generate weaker cellular influx, a trend that reached significance only for neutrophils (Fig. 2 a – e). Periodate-treated particles were nonetheless able to cause significant increases in eosinophils, neutrophils and MHCII- F4/80med macrophages. LPM disappearance was unaffected by periodate treatment (Fig. 2 f).