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Systematic Lupus Erythematosus (SLE) is an autoimmune syndrome of unclear etiology. While T and B cell abnormalities contribute to disease pathogenesis, recent work suggests that inflammatory M1-like macrophages also play a role. Previous work showed that the TLR2/1 agonist PAM3CSK4 (PAM3) could stimulate normal human monocytes to preferentially differentiate into immunosuppressive M2-like rather than inflammatory M1like macrophages. This raised the possibility of PAM3 being used to normalize the M1:M2 ratio in SLE. Consistent with that possibility, monocytes from lupus patients differentiated into M2-like macrophages when treated with PAM3 in vitro. Furthermore, lupus-prone NZB x NZW F1 mice responded similarly to weekly PAM3 treatment. Normalization of the M2 macrophage frequency was associated with delayed disease progression, decreased autoantibody and inflammatory cytokine synthesis, reduced proteinuria and prolonged survival in NZB x NZW F1 mice. The ability of PAM3 to bias monocyte differentiation in favor of immunosuppressive macrophages may represent a novel approach to the therapy of SLE. not support inflammatory responses. 'Non-classical' monocytes express a CD14 low CD16 + phenotype and are inflammatory. An 'intermediate' or transitional monocyte population also exists that is CD14 + CD16 + and has both phagocytic and inflammatory properties [7]. In response to stimulation, monocytes differentiate into macrophages with diverse phenotypes and functions. These range from 'classical' pro-inflammatory M1-like macrophages that protect the host from infection to 'alternatively activated' M2like macrophages that are immunosuppressive, support tissue remodeling, and phagocytose apoptotic cells [8-10]. Recent studies suggest that monocytes and macrophages can contribute to the pathogenesis of SLE. Indeed, lupus flares are associated with a relative increase in the frequency of M1 vs M2 macrophages [11]. The frequency of inflammatory monocytes is also elevated in SLE patients and the concentration of serum cytokines that promote macrophage differentiation (such as CSF-1 and MCP-1) correlates with disease severity [12]. Normalizing the M1:M2 ratio by adoptive transfer of M2 macrophages is of benefit

Inflammation of the gastrointestinal tract contributes to the development of inflammatory bowel disease (IBD). Human IBD is modeled by administering dextran sulfate sodium (DSS) to mice. In humans and mice, inflammatory M1 macrophages contribute to the progression of IBD whereas immunosuppressive M2 macrophages protect against colitis. The TLR2/1 agonist PAM3CSK4 (PAM3) induces human and murine monocytes to differentiate into immunosuppressive M2 macrophages, suggesting that PAM3 might be of benefit in the prevention/treatment of colitis. PAM3 was therefore administered to mice treated with DSS. As hypothesized, the number of M2 macrophages rose and disease severity decreased. The critical role of M2 macrophages in this process was established by transferring purified M2 macrophages from PAM3 treated control donors into DSS recipients and reducing colitis. These findings suggest that PAM3 may represent a novel approach to the treatment of human IBD. Ulcerative colitis and Crohn's disease are chronic inflammatory disorders of the gastrointestinal tract 1. In both types of IBD, activation of the innate rather than adaptive immune system is critical, with macrophages and dendritic cells contributing to the induction of inflammation 2-5. Intestinal macrophages occupy the interface between the host's GI tract and the resident microbiome. These macrophages can contribute to IBD pathogenesis by failing to eliminate inflammation-inducing microbes and/or failing to support the resolution of inflammation that arises via other mechanisms 6. The DSS-induced model of murine colitis is widely used to study human IBD due to its rapidity, simplicity and reproducibility. DSS disrupts the colonic epithelium and facilitates the invasion of intestinal microbes through the mucosa, causing inflammation characterized clinically by weight loss, diarrhea and rectal bleeding 7-9. 'Classical' or pro-inflammatory M1-like macrophages protect the host from infection whereas 'alternatively activated' M2-like macrophages act to suppress inflammation and support tissue remodeling 10-13. Studies suggest that M1 and M2 macrophages have opposing roles in DSS-induced colitis 14. M1 macrophages contribute to disease pathogenesis by secreting pro-inflammatory cytokines and causing tissue damage whereas M2 macrophages protect mice by secreting anti-inflammatory factors that aid in the resolution of inflammation 4,14-17. Depending upon the stimulus, monocytes can differentiate into either M1 or M2 macrophages. Our lab previously demonstrated that the TLR2/1 agonist PAM3CSK4 (PAM3) preferentially stimulated normal human and murine monocytes to mature into M2-like macrophages 10,18,19. The murine M2 macrophages co-expressed CD206 and F480. Purified cells of this phenotype were functionally M2 (based on their production of IL-10, phagocytic activity, and inability to produce inflammatory cytokines) 10. By comparison, F480 + macrophages that lacked CD206 were functionally M1 (producing IL-12 and IFNg, lysing tumor targets but lacking phagocytic activity) 18...

Synthetic oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODNs) stimulate immune cells via Toll-like receptor 9 (TLR9). Because oligodeoxynucleotides (ODNs) are susceptible to gastric degradation, clinical trials designed to evaluate their therapeutic utility have relied solely on parenteral routes of administration. A strategy to improve the activity of orally delivered ODNs by reducing their susceptibility to gastrointestinal (GI) digestion via encapsulation in calcium carbonate nanoparticles (ODNcaps) was recently described. This study compares the in vitro and in vivo activity of encapsulated (ODNcaps) versus free CpG ODNs delivered orally or parenterally. ODNcaps mirrored the ability of free ODNs to stimulate splenic B cells and macrophages in vitro. ODNcaps activated immune cells in the Peyer’s patches and mesenteric lymph nodes after oral delivery. Their effect on GI immunity was evaluated in studies of dextran sulfate sodium (DSS)-induced colitis and enteric infection, whereas systemic immunity was examined by monitoring their effect on lipopolysaccharide (LPS)-induced cytokine production and systemic pathogen challenge. Results indicate that orally delivered CpG ODNs predominantly induce GI rather than systemic immunity, and that calcium carbonate encapsulation does not significantly alter this behavior.