Journal d'immunobiologie

Dendritic cells (DCs) are important antigen-presenting cells of innate immune system. Their main function is to take up antigen and present it to T-cells to active adaptive immune response. The cytoskeletal proteins of the DCs not only maintain the morphology of DCs, but also are associated with the maturation and function of DCs. Additionally, rearrangement of cytoskeletal proteins is associated with viral infection in DCs. Regulating the specific cytoskeletal proteins of DCs would be a potential therapeutic strategy for preventing viral infection. Thus, the role of cytoskeletal proteins of DCs in immune response and viral infections were reviewed.

The activation of the platelet-activating factor receptor (PAFR) is associated to a suppressor phenotype in macrophages and dendritic cells (DCs). In the present study, we investigated mechanisms underlying the production of the interleukin 10 (IL-10) through PAFR activation in murine DCs. For this purpose, BALB/c mice bone marrow-derived DCs were differentiated by GM-CSF treatment and stimulated with LPS in the presence of the PAFR antagonist WEB2086. Signalling pathways downstream to TLR4 activation were investigated. We found that LPS stimulus induced PAFR ligands generation by DCs, but it did not affect the PAFR expression. The LPS-induced IL-10 production was found to be partially dependent of PAFR, since it was reduced in the presence of WEB2086. The IL-10 production through PAFR activation was independent on CREB and PPARγ, as the treatment with selective inhibitors of these pathways did not affect the IL-10 production. TLR4 adaptor molecules (MyD88 and TRIF) expression, MAPK, or NF-κB (p105/50 and p65 subunits) activation pathways were also excluded, since they were not affected by the treatment with WEB2086. The blockage of PAFR by WEB2086 downregulated the STAT3 (Tyr705) phosphorylation induced by LPS. Additionally, DCs treated with STAT3 inhibitor (S3I-201) showed reduced IL-10 production to the same levels observed in DCs treated with WEB2086. The requirement of STAT3 was confirmed in PAFR-KO DCs, since the STAT3 inhibition did not affect IL-10 production by these cells. Our data show an additional molecular mechanism whereby PAFR contributes to IL-10 production in DCs and support the importance of the PAFR activation in DCs phenotype and function.

Shortages in the availability of transplantable organs have forced the transplant community to seek alternative methods to increase the supply of available organs. In our recent study following α-1,3-galactocyltransferase knockout (GalT-KO) pig-to-baboon kidney xenotransplantation, we found that certain recipients developed increased serum creatinine, possibly due to the rapid growth of orthotopic pig grafts in smaller baboon recipients. To test our hypothesis, we assessed whether the growth of outbred (Yorkshire) organ transplants (kidney and lung) in miniature swine was regulated by intrinsic (graft) factors. Yorkshire kidneys reached 3.7x their initial volume over 3 months vs. 1.2x for miniature swine kidneys over a similar time period. A similar pattern was seen in porcine lung allografts as well. Following xenotransplantation, a review of our results suggests that there is a threshold for kidney graft volume of 25 cm3/kg of recipient body weight at which cortical ischemia is induced in transplanted GalT-KO kidneys in baboons. These results suggest that intrinsic factors are in part responsible for the growth of donor organs and this should be taken into consideration for growth-curve-mismatched transplants.

Aims: To unravel the cause and possible prevention of breast cancer, five potential polysaccharides from guava seed (GSPS), common buckwheat (CBPS), bitter buckwheat (BBPS), red Formosa lambsquarters (RFLPS) and yellow Formosa lambsquarters (YFLPS) were selected to treat human breast cancer MCF-7 cells with direct action or indirect tumor immunotherapy using polysaccharide-treated splenocyte-conditioned media (SCM).

Methods: Five different polysaccharides were partially characterized. Cytokine levels produced by type 1 helper T-cells [Th1; interleukin (IL)-2 and interferon-γ] and type 2 helper T-cells (Th2; IL-4, IL-5 and IL-10) in SCM were determined using ELISA. Breast cancer MCF-7 cell viability was determined using an MTT assay. The association between cytokine levels in SCM and the corresponding breast cancer MCF-7 cell viability was investigated using the Pearson product-moment correlation coefficient.

Results: Total carbohydrate and protein contents indicated that these isolated polysaccharides might be proteopolysaccharides or glycoproteins. Molecular weights of purified polysaccharides fractions from the five isolated polysaccharides were determined. All 5 selected crude polysaccharides, in particular GSPS, BBPS and RFLPS, significantly increased IL-10/IL-2 cytokine secretion ratios by splenocytes. Treatment with SCM prepared in the presence or absence of the polysaccharides, but not the direct action of the polysaccharides, significantly inhibited MCF-7 cell viability. GSPS-, BBPS- and RFLPS-treated SCM demonstrated slightly enhanced inhibitory effects against breast cancer MCF-7 cell viability. There were negative correlations between MCF-7 cell viabilities and IL-10 cytokine secretion levels, as well as IL-10/IL-2 cytokine secretion ratios in the corresponding SCM. The present findings suggested that an increased Th2/Th1 cytokine secretion ratio, particularly an increase in IL-10, by immune cells including T lymphocytes, may inhibit MCF-7 cell growth in the tumor microenvironment. GSPS, BBPS and RFLPS may be further applied to treat human breast cancer via tumor immunotherapy by increasing the Th2/ Th1 cytokine secretion ratio.