Lymphocytes travel throughout the body to carry out immune surveillance and participate in inflammatory reactions. Their path takes them from blood through tissues into lymph and back to blood. Molecules that control lymphocyte recruitment into extralymphoid tissues are well characterized, but exit is assumed to be random. Here, we showed that lymphocyte emigration from the skin was regulated and was sensitive to pertussis toxin. CD4(+) lymphocytes emigrated more efficiently than CD8(+) or B lymphocytes. T lymphocytes in the afferent lymph expressed functional chemokine receptor CCR7, and CCR7 was required for T lymphocyte exit from the skin. The regulated expression of CCR7 by tissue T lymphocytes may control their exit, acting with recruitment mechanisms to regulate lymphocyte transit and accumulation during immune surveillance and inflammation.

B cells infiltrate the skin in many chronic inflammatory diseases caused by autoimmunity or infection. Despite potential contribution to disease, skin-associated B cells remain poorly characterized. Using an ovine model of granulomatous skin inflammation, we demonstrate that B cells increase in the skin and skin-draining afferent lymph during inflammation. Surprisingly, skin B cells are a heterogeneous population that is distinct from lymph node B cells, with more large lymphocytes as well as B-1-like B cells that co-express high levels IgM and CD11b. Skin B cells have increased MHCII, CD1, and CD80/86 expression compared with lymph node B cells, suggesting that they are well-suited for T cell activation at the site of inflammation. Furthermore, we show that skin accumulation of B cells and antibody-secreting cells during inflammation increases local antibody titers, which could augment host defense and autoimmunity. While skin B cells express typical skin homing receptors such as E-selectin ligand and alpha-4 and beta-1 integrins, they are unresponsive to ligands for chemokine receptors associated with T cell homing into skin. Instead, skin B cells migrate toward the cutaneously expressed CCR6 ligand CCL20. Our data support a model in which B cells use CCR6-CCL20 to recirculate through the skin, fulfilling a novel role in skin immunity and inflammation.

No abstract

Substantial evidence for prion transmission via blood transfusion exists for many transmissible spongiform encephalopathy (TSE) diseases. Determining which cell phenotype(s) is responsible for trafficking infectivity has important implications for our understanding of the dissemination of prions, as well as their detection and elimination from blood products. We used bioassay studies of native white-tailed deer and transgenic cer- Chronic wasting disease (CWD) is an infectious proteinmisfolding disease, or transmissible spongiform encephalopathy (TSE), affecting cervids in North America (59, 76-79) and one Asian country (41,68). CWD is unique among prion diseases in affecting free-ranging wildlife populations (deer, elk, and moose). Early and subsequent observations made by Williams and Miller (58,79) related CWD transmission to direct contact with clinically affected deer, as well as indirect contact with environments previously populated by infected deer (57). Bioassay studies of white-tailed deer have demonstrated that body fluids and excreta (saliva, urine, feces, and blood) contain infectious prions (53, 54). Both clinical and preclinical CWDinfected deer harbored sufficient infectious prions to produce CWD in naïve white-tailed deer following ingestion of saliva or transfusion of whole blood (53, 54).The detection of blood-borne infectious prions has important implications for our understanding of the spread of prions among and within individuals, as well as for the elimination of prions from blood products (13,15,33,45), given the evidence for Creutzfeldt-Jakob disease (CJD) transmission via blood transfusion (16,29,47,50,62,72,73). Identifying the cell phenotype or cell-free protein fractions that harbor prion infectivity would contribute importantly to this understanding and to the development of blood-based assays to detect prion infection. We undertook the present studies to address these issues. MATERIALS AND METHODSBioassay studies of white-tailed deer. White-tailed deer fawns were provided by the Warnell School of Forestry and Natural Resources, University of Georgia, Athens-a region in which CWD has not been detected. The deer fawns were hand raised and human and indoor adapted before overnight transport directly to the Colorado State University (CSU) CWD research indoor isolation facility without contact with the native Colorado environment. The 4-month-old fawns were adapted to the facility housing conditions and diet for 2 months before the study start.Genotyping. All white-tailed deer were genotyped to determine their GG/GS (codon 96) status by the laboratory of Katherine O'Rourke, USDA-ARS, Pullman, WA. Deer were allocated into inoculation cohorts (n ϭ 4) without knowledge of their G96 genotypes.Biocontainment protocols. Protocols to preclude extraneous exposure and cross contamination between cohorts of animals as previously described (53, 54) incorporated protective shower-in requirements, Tyvek clothing, masks, head covers, and footwear while maintaining stringent husbandry. Tonsil biopsy ...

We investigated lymphatic drainage pathways of the central nervous system in conscious sheep and quantified the clearance of a cerebrospinal fluid (CSF) tracer into lymph and blood. In the first group of studies, 125I-HSA was injected into the lateral ventricles of the brain or into lumbar CSF and after 6 h, various lymph nodes and tissues were excised and counted for radioactivity. Multiple lymphatic drainage pathways of cranial CSF existed in the head and neck region defined by elevated 125I-HSA in the retropharyngeal/cervical, thymic, pre-auricular and submandibular nodes. Implicated in spinal CSF drainage were mainly the lumbar and intercostal nodes. In a second group of experiments, multiple cervical vessels and the thoracic duct were cannulated and lymph diverted from the animals. Transport of tracer through arachnoid villi was taken from recoveries in venous blood. Following intraventricular administration, the 6 h recoveries of 125I-HSA in the lymph (sum of cervical and thoracic duct) and blood were 8.2% +/- 3.0 and 12.5% +/- 4.5 respectively and at 22 h, 25.1% +/- 6.9 and 20.8% +/- 4.1 respectively. When 125I-HSA was injected into lumbar CSF, the 6 h recoveries of tracer in thoracic duct and blood were 11.6% +/- 2.7 and 16.3% +/- 3.7 respectively. Total lymph and blood recoveries were not significantly different in any experiment. We conclude that the clearance of 125I-HSA from the CSF is almost equally distributed between lymphatic and arachnoid villi pathways.