Immunotherapy-on-Chip Against an Experimental Sepsis Model.

Lipopolysaccharide (LPS) is commonly used in murine sepsis models, which are largely associated with immunosuppression and collapse of the immune system. After adapting the LPS treatment to the needs of locally bred BALB/c mice, the present study explored the protective role of Micrococcus luteus peptidoglycan (PG)-pre-activated vaccine-on-chip technology in endotoxemia. The established protocol consisted of five daily intraperitoneal injections of 0.2 µg/g LPS, allowing longer survival, necessary for a therapeutic treatment application. A novel immunotherapy technology, the so-called vaccine-on-chip, consists of a 3-dimensional laser micro-textured silicon (Si) scaffold loaded with macrophages and activated in vitro with 1 µg/ml PG, which has been previously shown to exert a mild immunostimulatory activity upon subcutaneous implantation. The LPS treatment significantly decreased CD4 + and CD8 + cells, while increasing CD11b + , Gr1 + , CD25 + , Foxp3 + , and class II + cells. These results were accompanied by increased arginase-1 activity in spleen cell lysates and C-reactive protein (CRP), procalcitonin (PCT), IL-6, TNF-a, IL-10, and IL-18 in the serum, while acquiring severe sepsis phenotype as defined by the murine sepsis scoring. The in vivo application of PG pre-activated implant significantly increased the percentage of CD4 + and CD8 + cells, while decreasing the percentage of Gr1 + , CD25 + , CD11b + , Foxp3 + cells, and arginase-1 activity in the spleen of LPS-treated animals, as well as all serum markers tested, allowing survival and rescuing the severity of sepsis phenotype. In conclusion, these results reveal a novel immunotherapy technology based on PG pre-activated micro-texture Si scaffolds in LPS endotoxemia, supporting thus its potential use in the treatment of septic patients.

Serum-derived MHC class II molecules: potent regulators of the cellular and humoral immune response.

Soluble MHC antigens are detected in body fluids but their role and origin are still unclear. This study examined whether serum IA antigens, isolated from BALB/c mice (sIA(d)), could modulate the immune response. Specific purification procedures isolated intact IA molecules, which were thereafter applied to functional assays. Thus, sIA(d) were shown to stimulate spleen cell proliferation and the major target was identified to be the CD4(+) cell population. Inhibition of the CD4 co-receptor using specific neutralizing antibodies destroyed the sIA(d)-mediated proliferative activity, while sIA(d) successfully antagonized surface IA(d) antigens for binding to anti-IA(d) antibody. Serum-IA(d) stimulated BALB/c versus C3H/HeN but not C3H/HeN versus BALB/c mixed lymphocyte reactions, while increasing responsiveness to Legionella pneumophila. However, sIA(d) displayed an inhibitory activity during the effector phase of the humoral response, since they inhibited the anti-DNP-specific IgM production to a DNP-HSA hapten-carrier system. Furthermore, sIA(d) molecules increased Th1/Th2 cytokines during the L. pneumophila stimulus, while decreasing IL-2, GM-CSF and increasing IL-4, IL-15 during the DNP-HSA stimulus. These results suggest that sIA(d), following steps similar to surface class II antigen binding mechanisms, stimulate the initiation of a humoral or cellular immune response but rather inhibit the effector phase of the reactions, attributing thus soluble class II MHC antigens important immunomodulatory roles.