NIH conference. Lupus nephritis

Nephritis has long been considered one of the most ominous components of systemic lupus erythematosus. Accumulations of immune complexes and lymphoid cells in several locations within the kidney are the best-described elements of lupus nephritis. The extreme diversity of the renal changes indicates that many variables are likely to be involved. Inbred strains of lupus-prone mice have provided homogeneous subjects for study of pathogenesis and response to treatment. Comparable grouping of lupus nephritis in humans according to unique or dominant pathogenetic mechanisms is imprecise and limited by insufficient knowledge of the primary stimulus for the disease. Treatment is also imperfect and, at times, hazardous. Certain regimens incorporating cytotoxic drugs provide a significant therapeutic advantage over corticosteroids alone in the management of this disease.     

Can Achilles and patellar tendon structures predict musculoskeletal injuries in combat soldiers?

Aiming to investigate whether Achilles tendon (AT) structure and patellar tendon (PT) structure are risk factors for musculoskeletal injuries in combat soldiers, 168 participants were recruited from an infantry commander's course. The AT and PT were examined pre‐course using UTC to capture the structure of four echo‐type fibers (I–IV). All injuries were assessed by military physicians pre‐course and throughout the 14‐week course. Soldiers who were injured during the course had a significantly higher pre‐course prevalence of AT and PT echo‐type III and echo‐type IV compared to soldiers that were not injured during the course. Variables that were found to be associated with injured/non‐injured participants were echo‐type III + IV of the PT (OR = 1.44, 95% CI = 1.24‐1.68) and echo‐type III of the AT (OR = 1.69, 95% CI = 1.35‐2.12). ROC analyses showed that the best model, exhibiting both high sensitivity and low specificity, was that participants with PT echo‐type III + IV > 10% or AT echo‐type III >8.5% had the highest risk of being injured during the course. In conclusions, the tendon structure at the beginning of high‐intensity activity or physical training program might be a risk factor for subsequent injury during the course. Soldiers and high‐level athletes should be aware of the cutoff points for fiber types in tendon structure that might put them at high risk for future injury. At‐risk soldiers/athletes should be provided with an intervention program before they start their training program, with the aim of improving the tendon structure and preventing subsequent injury.     

Evidence that Meningeal Mast Cells Can Worsen Stroke Pathology in Mice

Stroke is the leading cause of adult disability and the fourth most common cause of death in the United States. Inflammation is thought to play an important role in stroke pathology, but the factors that promote inflammation in this setting remain to be fully defined. An understudied but important factor is the role of meningeal-located immune cells in modulating brain pathology. Although different immune cells traffic through meningeal vessels en route to the brain, mature mast cells do not circulate but are resident in the meninges. With the use of genetic and cell transfer approaches in mice, we identified evidence that meningeal mast cells can importantly contribute to the key features of stroke pathology, including infiltration of granulocytes and activated macrophages, brain swelling, and infarct size. We also obtained evidence that two mast cell-derived products, interleukin-6 and, to a lesser extent, chemokine (C-C motif) ligand 7, can contribute to stroke pathology. These findings indicate a novel role for mast cells in the meninges, the membranes that envelop the brain, as potential gatekeepers for modulating brain inflammation and pathology after stroke.Stroke, the leading cause of adult disability and the fourth most common cause of death in the Unites States,^1,2 occurs when there is insufficient blood flow to the brain, and the resultant injury initiates a cascade of inflammatory events, including immune cell infiltration into the brain.^3–5 This post-stroke inflammation is a critical determinant of damage and recovery after stroke; understanding the interplay between the immune system and the brain after stroke holds much promise for therapeutic intervention.^4–7 However, successfully exploiting this therapeutic potential requires a detailed understanding of the interplay between the immune system and the brain after stroke.⁴An understudied but important aspect of this interplay is the role of meningeal-located immune cells in modulating brain pathology. The meninges have long been recognized as an anatomical barrier that protects the central nervous system (CNS). However, accumulating evidence suggests that the meninges are important for communication between the CNS and immune system during health and disease.^8–10 All blood vessels pass through the meningeal subarachnoid space before entering the brain, and this vascular connection and the close proximity of the meninges to the underlying parenchymal nervous tissue make them ideally located to act as a gatekeeper to modulate immune cell trafficking to the CNS. To support this gatekeeper function is evidence that the meninges modulate brain infiltration of T cells, neutrophils, and monocytes during meningitis and autoimmune conditions,^11–14 with immune cells observed in some instances accumulating in the meninges before they infiltrate into the parenchyma.^11,13Emerging evidence suggests that the actions of immune cells resident in the meninges are important for this gatekeeper function.^11,12,15 Mast cells (MCs), best known as proinflammatory effector cells, can play critical roles in the development of inflammation in many disease settings.^16–18 MCs reside in high numbers within the meninges, but their function in this site has not been fully investigated in stroke pathology. Unlike most immune cells, mature MCs do not circulate in the blood but are long-term residents of tissues, often in perivascular locations, and can rapidly perform their functions in situ. CNS MCs are found in the brain parenchyma and the meninges of rodents and humans.¹⁸ It has been proposed that brain parenchymal MCs can enhance brain neutrophil numbers after stroke and can exacerbate stroke pathology.^19–24 However, much of the evidence to support such conclusions is indirect. For example, some of the studies that implicate MCs in stroke pathology used pharmacologic approaches to interfere with MC activation,^19,20,22 but such drugs can have effects on other cell types.²⁵ Moreover, the role of the meningeal MCs in modulating post-stroke inflammation and pathology is unknown. Finally, little is understood about which among the many MC-derived mediators may be important in stroke pathology.^17,26To address these questions, we used genetic and cell transfer approaches to study the role of MCs in the pathology of ischemic stroke in mice. Specifically, we tested a c-kit–mutant mouse model (ie, WBB6F₁-Kit^W/W-v mice) which is profoundly MC deficient and can be repaired of this deficiency by engraftment of in vitro-derived MCs from wild-type (WT) mice. This MC knock-in approach enables the MC-dependent effects in the mutant mice to be separated from effects due to other abnormalities associated with their mutation,^11,17,26,27 because only the MC deficiency is repaired by MC engraftment. Furthermore, one can investigate the mechanisms by which MCs influence stroke pathology by engrafting MCs from transgenic mice that lack specific MC-associated products. We also tested our newly described Cpa3-Cre; Mcl-1^fl/fl mice, in which MC (and basophil) numbers are reduced constitutively via Cre-mediated depletion of the anti-apoptotic factor, myeloid cell leukemia sequence 1 (Mcl-1), in the affected lineages.²⁸ Cpa3-Cre; Mcl-1^fl/fl mice lack the other abnormalities associated with the c-kit mutations in WBB6F₁-Kit^W/W-v mice.²⁸With the use of these in vivo models, we identified meningeal MCs as important contributors to key features of stroke pathology, including increased numbers of brain granulocytes and activated macrophages, brain swelling, and infarct size. We also obtained evidence that two potentially proinflammatory MC-derived products, IL-6 and, to a lesser extent, chemokine (C-C motif) ligand 7 (CCL7), can contribute to pathology in this setting.