Lymphoid Structures (lymphoid + structure)

Distribution by Scientific Domains

Selected Abstracts

Lymphoid microenvironment in the gut for immunoglobulin A and inflammation

Robert Chin
Summary:, Signaling through lymphotoxin , receptor (LT,R) initiates the unfolding of a host of developmental programs ranging from the organogenesis of lymph nodes and Peyer's patches (PPs) to the coordination of splenic microarchitecture. While investigating an alternative pathway to immunoglobulin A (IgA) production, it was uncovered that LT,R signaling in the lamina propria (LP) stroma orchestrates the coordinated expression of key chemokines and adhesion molecules, creation of a cytokine milieu, and stroma development that facilitates robust IgA production independent of secondary lymphoid structures. Simultaneously, this same infrastructure can be commandeered by autoreactive T cells to organize both the acute destruction of the intestinal mucosa and chronic intestinal inflammation via the ligands for LT,R. The ability to modulate LT,R signaling may alternatively permit the suppression of autoimmune responses and augmentation of gut defenses. [source]

The mucosal immune system

Thomas T. MacDonald
SUMMARY This article outlines the lymphoid structures and cell types important in the intestinal immune response. Particular attention is paid to differences between rodents and man where there appears to be fundamental differences in the sources of the T and B cells which populate the mucosa. The majority of the data still suggest that Peyer's patches are the inductive site of mucosal immunity and the mucosa (lamina propria and epithelium) is the effector site, but there is growing realization that mucosal immune responses can occur in the absence of Peyer's patches and that antigen sampling may also occur in the lamina propria. [source]

Presence of Subepithelial Lymphoid Nodules in the Teat of Ewes

V. S. Mavrogianni
Summary A total of 87 clinically healthy ovine teats were examined bacteriologically (by scraping the mucosa) and histologically. Teats examined were those of lactating mammary glands with no bacteria isolated (n = 23); of mammary glands after cessation of lactation with no bacteria isolated (n = 25); of lactating mammary glands with bacteria isolated (n = 22); and of mammary glands after cessation of lactation with bacteria isolated (n = 17). The salient histological feature was subepithelial leucocytic infiltration. In teat cisterns, lymphocytes were the predominant cell type and in teat ducts, lymphocytes and neutrophils were seen in equal proportions. Subepithelial lymphoid nodules, some with germinal centres, were detected in 43 (49%) teats. The majority of lymphoid nodules was observed at the border between teat duct and teat cistern. Presence of bacteria was significantly associated with the presence of leucocytic activity (P < 0.001) and with the presence of lymphoid nodules (P = 0.032). We conclude that the presence of induced subepithelial lymphoid tissue at the border between teat duct and teat cistern appears to be important in protecting the mammary gland during the early stages of bacterial invasion. The findings call for further investigations into the lymphoid structures of the teat; these should elucidate the role and development of mammary mucosa-associated lymphoid tissues and may lead to strategies for enhancing non-specific defence mechanisms of the mammary gland. [source]

Extranodal lymphoid microstructures in inflamed muscle and disease severity of new-onset juvenile dermatomyositis,

Consuelo M. López De Padilla
Objective Juvenile dermatomyositis (DM) is an autoimmune disease of childhood characterized by lesions in skin and muscle that are populated by plasmacytoid dendritic cells (PDCs) and lymphocyte infiltrates. We undertook this study to examine the cellular composition, organization, and molecular milieu of the cellular infiltrates in muscle in juvenile DM and to correlate the infiltrates with clinical disease manifestations. Methods Since PDCs and lymphocyte foci express CCL19 and CCL21, we investigated for in situ formation of lymphoid microstructures that could be sites of extranodal immune activation. Results Analyses of muscle biopsy samples from children with new-onset juvenile DM showed 3 categories of lesions: diffuse infiltrates, lymphocytic aggregates lacking follicle-like organization, and follicle-like structures. The last of these exhibited elements of classic lymphoid follicles, including networks of follicular dendritic cells and high endothelial venules. They also expressed high levels of CXCL13 and lymphotoxins known to support lymphoid organogenesis. There were also resident naive CD45RA+ T cells and maternally derived B cells and PDCs. Patients with diffuse infiltrates or lymphocytic aggregates were responsive to standard therapy with steroids and methotrexate, but those with follicle-like structures tended to have severe disease that required additional agents such as intravenous Ig or rituximab. Conclusion These data suggest that lymphoneogenesis is a component of the early disease process in juvenile DM. Ectopic lymphoid structures could indicate a severe course of disease; their early detection could be a tool for disease management. [source]