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).