A novel model for lymphocytic infiltration of the thyroid gland generated by transgenic expression of the CC chemokine CCL21

Lymphocytic infiltrates and lymphoid follicles with germinal centers are often detected in autoimmune thyroid disease (AITD), but the mechanisms underlying lymphocyte entry and organization in the thyroid remain unknown. We tested the hypothesis that CCL21, a chemokine that regulates homeostatic lymphocyte trafficking, and whose expression has been detected in AITD, is involved in the migration of lymphocytes to the thyroid. We show that transgenic mice expressing CCL21 from the thyroglobulin promoter (TGCCL21 mice) have significant lymphocytic infiltrates, which are topologically segregated into B and T cell areas. Although high endothelial venules expressing peripheral lymph node addressin were frequently observed in the thyroid tissue, lymphocyte recruitment was independent of L-selectin or lymphotoxin-α but required CCR7 expression. Taken together, these results indicate that CCL21 is sufficient to drive lymphocyte recruitment to the thyroid, suggest that CCL21 is involved in AITD pathogenesis, and establish TGCCL21 transgenic mice as a novel model to study the formation and function of lymphoid follicles in the thyroid

CD169(+) macrophages provide a niche promoting erythropoiesis under homeostasis and stress

The role of macrophages in erythropoiesis was suggested several decades ago with the description of “erythroblastic islands” in the bone marrow (BM) composed of a central macrophage surrounded by developing erythroblasts. However, the in vivo role of macrophages in erythropoiesis under homeostasis or disease remains unclear. Specific depletion of CD169(+) macrophages markedly reduced erythroblasts in the BM but did not result in overt anemia under homeostasis likely due to concomitant alterations in RBC clearance. However, CD169(+) macrophage depletion significantly impaired erythropoietic recovery from hemolytic anemia, acute blood loss and myeloablation. Furthermore, macrophage depletion normalized the erythroid compartment in a JAK2(V617F)-driven murine model of polycythemia vera (PV), suggesting that erythropoiesis in PV, unexpectedly, remains under the control of macrophages in the BM and splenic microenvironments. These data indicate that CD169(+) macrophages promote late erythroid maturation and that modulation of the macrophage compartment represents a novel strategy to treat erythropoietic disorders

Rhythmic Modulation of the Hematopoietic Niche through Neutrophil Clearance

SummaryUnique among leukocytes, neutrophils follow daily cycles of release from and migration back into the bone marrow, where they are eliminated. Because removal of dying cells generates homeostatic signals, we explored whether neutrophil elimination triggers circadian events in the steady state. Here, we report that the homeostatic clearance of neutrophils provides cues that modulate the physiology of the bone marrow. We identify a population of CD62LLO CXCR4HI neutrophils that have “aged” in the circulation and are eliminated at the end of the resting period in mice. Aged neutrophils infiltrate the bone marrow and promote reductions in the size and function of the hematopoietic niche. Modulation of the niche depends on macrophages and activation of cholesterol-sensing nuclear receptors and is essential for the rhythmic egress of hematopoietic progenitors into the circulation. Our results unveil a process that synchronizes immune and hematopoietic rhythms and expand the ascribed functions of neutrophils beyond inflammation.PaperFlic

WINNING, LOSING, AND STILL PLAYING THE GAME: THE POLITICAL ECONOMY OF IMMIGRATION IN CANADA

In contrast to most other countries, public opinion in Canada is relatively positive towards immigration and immigrants. Yet the economic fortunes of immigrants, especially those who have arrived recently, have been falling over the past three decades. Four analytical perspectives on the relatively poor economic performance of immigrants in Canada are discussed, and are used to build a composite understanding of this economic outcome. I argue that the weak economic position of immigrants - particularly the fact that they do not compete against the Canadian-born in privileged segments of the labour market - is an important ingredient in the favourable public view of immigration. Copyright (c) 2006 by the Royal Dutch Geographical Society KNAG.

Roadmap for the Emerging Field of Cancer Neuroscience

Mounting evidence indicates that the nervous system plays a central role in cancer pathogenesis. In turn, cancers and cancer therapies can alter nervous system form and function. This Commentary seeks to describe the burgeoning field of "cancer neuroscience" and encourage multidisciplinary collaboration for the study of cancer-nervous system interactions

Inflammatory exposure drives long-lived impairment of hematopoietic stem cell self-renewal activity and accelerated aging

Hematopoietic stem cells (HSCs) mediate regeneration of the hematopoietic system following injury, such as following infection or inflammation. These challenges impair HSC function, but whether this functional impairment extends beyond the duration of inflammatory exposure is unknown. Unexpectedly, we observed an irreversible depletion of functional HSCs following challenge with inflammation or bacterial infection, with no evidence of any recovery up to 1 year afterward. HSCs from challenged mice demonstrated multiple cellular and molecular features of accelerated aging and developed clinically relevant blood and bone marrow phenotypes not normally observed in aged laboratory mice but commonly seen in elderly humans. In vivo HSC self-renewal divisions were absent or extremely rare during both challenge and recovery periods. The progressive, irreversible attrition of HSC function demonstrates that temporally discrete inflammatory events elicit a cumulative inhibitory effect on HSCs. This work positions early/mid-life inflammation as a mediator of lifelong defects in tissue maintenance and regeneration