Genetic associations between rheumatoid arthritis and specific HLA class II genes provide clues to understanding the molecular basis for disease susceptibility. There is a remarkable structural relationship among different rheumatoid arthritis (RA) susceptibility genes, in which each of the associated class II alleles encodes a sequence of key amino acids termed the 'shared epitope.' Mechanistic models to account for the shared epitope association with RA can be interpreted in the context of an HLA-directed pathway for the development of disease. We suggest that altered T cell activation results from recognition of the shared epitope, providing a potential mechanism by which the shared epitope may be involved in the generation or modulation of self-recognition during antigen presentation and processing. We propose that the shared epitope association with RA is not solely based on a specific peptide binding motif and peptide determinant selection but rather is influenced by a strongly biased direct recognition of shared epitope residues by direct T cell contact. 1. Nepom GT: Major histocompatibility complex-directed susceptibility to rheumatoid arthritis.

Utilizing immunocytochemistry numerous macrophages were localized in regressing corpora lutea. In contrast, few macrophages were observed in young corpora lutea. Regressing corpora lutea readily produced TNF-a in vitro in response to lipopolysaccharide, whereas young corpora lutea produced significantly less TNF-a. T lymphocytes were identified in young corpora lutea preceding the appearance of macrophages. These observations suggest that cells of the immune system and cytokines could be important participants in physiological regression of the corpus luteum.

Single injections of recombinant cytokines/chemokines into tissue have provided insights into their possible roles during the inflammatory response. Adenoviral technology may allow us to mimic the in vivo situation more closely, with protein generated in a continuous but transient fashion. Replication-deficient human type 5 adenovirus containing a rat macrophage inflammatory protein-2 (MIP-2) gene insertion and cytomegalovirus promoter was injected into the mouse brain to investigate the inflammatory response to continuous overproduction of MIP-2. Adenovirus with a LacZ gene insertion expressing beta-galactosidase was used as a control. At doses of 10(4) to 10(7) plaque-forming units, a minimal inflammatory response was detected to the LacZ virus, with leukocyte recruitment that was restricted to the injection site. A dose of 10(7) plaque-forming units of both the LacZ and the MIP-2 vector produced extensive transgene product expression that persisted for at least 7 days. Astrocytes, recognized by their morphology, were the predominant cell type expressing MIP-2 and beta-galactosidase. A dose of 10(7) plaque-forming units of MIP-2 vector caused dramatic polymorphonuclear leukocyte (PMN) recruitment to the brain parenchyma after 2 days. PMN recruitment was still observed after 4 and 7 days, but had become more localized to the injection site and was associated with numerous foam-like macrophages. At both 2 and 7 days the blood-brain barrier was breached in the region of leukocyte recruitment. Despite the extent of leukocyte recruitment there were no overt signs of neuronal degeneration or demyelination. Our findings demonstrate that continuous production of MIP-2 in the CNS results in persistent PMN recruitment to the brain parenchyma with no evidence of tachyphylaxis. The lack of PMN recruitment to the brain parenchyma following CNS injury may be a result of deficient production of PMN chemoattractants.

Polymorphonuclear neutrophils (PMN) have been implicated in the pathogenesis of emphysema. The chemokines interleukin-8(IL-8), growth-related oncogene (GRO-alpha) and extractable nuclear antigen (ENA)-78 may be involved in the increased numbers of PMN in smokers' airspaces. The levels of these cytokines in bronchoalveolar lavage fluid (BALF) and bronchoalveolar lavage leukocyte conditioned medium (LCM), along with BALF PMN numbers in 12 smokers who abstained for 12 h (chronic smoking) or continued to smoke until I h before study (acute smoking) and seven nonsmokers were compared. Neutrophils in BALF increased in acute (1.96+/-0.53%, 0.99+/-0.32x10(6) cells) compared with chronic smokers (0.59+/-0.25%, 0.61+/-0.24x10(6) cells, p<0.05 nonsmokers) and nonsmokers (0.79+/-0.29%, 0.05+/-0.01x 10(6) cells, p<0.05). There were no differences in IL-8 or GRO-alpha in BALF between smokers and nonsmokers. ENA-78 levels were lower in smokers (p=0.006). There was no difference in IL-8, GRO-alpha or ENA-78 in LCM from unstimulated cells in smokers versus nonsmokers. After stimulation with lipopolysaccharide (LPS) 10 ng mL(-1), IL-8 release in acute smokers (p=0.04) and GRO-alpha release in smokers (p=0.009) were significantly higher than in nonsmokers. Following stimulation with LPS 100 ng.mL(-1), GRO-alpha release was higher in smokers (p=0.03) and increased further in acute smokers (p=0.02 versus nonsmokers, p=0.04 versus chronic smokers) and ENA-78 release increased in smokers (p=0.02 versus non-smokers). In conclusion, influx of polymorphonuclear neutrophils into smokers' airspaces is an acute phenomenon and neutrophil chemokine release from mixed bronchoalveolar lavage leukocytes is influenced by cigarette smoking and endotoxins.

Macrophages are critical for the initiation and resolution of the inflammatory phase of wound healing. In diabetes, macrophages display a prolonged inflammatory phenotype preventing tissue repair. TLRs, particularly TLR4, have been shown to regulate myeloid-mediated inflammation in wounds. We examined macrophages isolated from wounds of patients afflicted with diabetes and healthy controls as well as a murine diabetic model demonstrating dynamic expression of TLR4 results in altered metabolic pathways in diabetic macrophages. Further, using a myeloid-specific mixed-lineage leukemia 1 (MLL1) knockout (Mll1 f/f Lyz2 Cre+ ), we determined that MLL1 drives Tlr4 expression in diabetic macrophages by regulating levels of histone H3 lysine 4 trimethylation on the Tlr4 promoter. Mechanistically, MLL1-mediated epigenetic alterations influence diabetic macrophage responsiveness to TLR4 stimulation and inhibit tissue repair. Pharmacological inhibition of the TLR4 pathway using a small molecule inhibitor (TAK-242) as well as genetic depletion of either Tlr4 (Tlr4 2/2 ) or myeloid-specific Tlr4 (Tlr4 f/f Lyz2 Cre+ ) resulted in improved diabetic wound healing. These results define an important role for MLL1-mediated epigenetic regulation of TLR4 in pathologic diabetic wound repair and suggest a target for therapeutic manipulation.