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John B.,University of Pennsylvania | Ricart B.,University of Pennsylvania | Wojno E.D.,University of Pennsylvania | Harris T.H.,University of Pennsylvania | And 7 more authors.
PLoS Pathogens | Year: 2011

Under normal conditions the immune system has limited access to the brain; however, during toxoplasmic encephalitis (TE), large numbers of T cells and APCs accumulate within this site. A combination of real time imaging, transgenic reporter mice, and recombinant parasites allowed a comprehensive analysis of CD11c + cells during TE. These studies reveal that the CNS CD11c + cells consist of a mixture of microglia and dendritic cells (DCs) with distinct behavior associated with their ability to interact with parasites or effector T cells. The CNS DCs upregulated several chemokine receptors during TE, but none of these individual receptors tested was required for migration of DCs into the brain. However, this process was pertussis toxin sensitive and dependent on the integrin LFA-1, suggesting that the synergistic effect of signaling through multiple chemokine receptors, possibly leading to changes in the affinity of LFA-1, is involved in the recruitment/retention of DCs to the CNS and thus provides new insights into how the immune system accesses this unique site. © 2011 John et al.

PubMed | The Centenary Institute for Cancer Medicine and Cell Biology
Type: Journal Article | Journal: Immunology and cell biology | Year: 2012

Aging has profound effects on the immune system, including thymic involution, reduced diversity of the T cell receptor repertoire, reduced effector T cell and B cell function and chronic increase of proinflammatory cytokine production by innate immune cells. The precise effects of aging on conventional dendritic cells (cDC), the main antigen presenting cells of the immune system, however, are not well understood. We found that in aged mice the number of cDC in the spleen and lymph nodes remained stable, whereas the number of cDC in the lungs increased with age. Whereas cDC in mice showed similar cycling kinetics in all organs tested, cDC reconstitution by aged bone marrow precursors was relatively higher than that of their young counterparts. With the exception of CD86, young and aged cDC did not differ in their expression of co-stimulatory molecules at steady state. Most toll-like receptor (TLR) ligands induced comparable upregulation of co-stimulatory molecules CD40, CD86 and B7H1 on young and aged cDC, whereas TLR2 and TLR5 stimulation resulted in reduced upregulation of CD80 and CD86 on aged cDC in vitro. In vivo, influenza infection-induced upregulation of CD86, but not other co-stimulatory molecules, was lower in aged DC. Young and aged DC were equally capable of direct and cross presentation of antigens in vitro. Transcriptome analysis did not reveal any significant difference between young and aged cDC. These data show that unlike T and B cells, the maintenance of cDC throughout the life of a healthy animal is relatively robust during the aging process.

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