Lymphocyte homing to secondary lymphoid tissue is defined by a multistep sequence of interactions between lymphocytes and endothelial cells in high endothelial venules (HEVs). After initial selectin-mediated tethering and rolling, firm adhesion of lymphocytes requires rapid upregulation of lymphocyte integrin adhesiveness. This step is mediated in part by the HEV-derived chemokine SLC (secondary lymphoid-tissue chemokine, or CCL21) that binds to the CC chemokine receptor (CCR)7 on lymphocytes. However, the CC chemokine ELC (Epstein-Barr virus–induced molecule 1 ligand chemokine, or CCL19) shares the same receptor, and ELC transcripts have been observed in the T cell areas of lymphoid organs. Here, we show that perivascular ELC is transcytosed to the luminal surfaces of HEVs and enables efficient T cell homing to lymph nodes. In situ hybridization on sections of human tonsil showed no ELC mRNA in HEVs, but immunostaining revealed ELC protein in cytoplasmic vesicles of HEV cells. Furthermore, ELC injected into the footpads of mice entered the draining lymph nodes and was presented by HEVs. Finally, intracutaneous injections of ELC in mice lacking functionally relevant ELC and SLC (plt/plt mice) restored T cell trafficking to draining lymph nodes as efficiently as SLC. We conclude that perivascular ELC is transcytosed to the luminal surfaces of HEVs and participates in CCR7-mediated triggering of lymphocyte arrest.

IntroductionRheumatoid arthritis (RA) and ulcerative colitis (UC) are chronic inflammatory diseases associated with de novo formation of irregular T-and B-cell aggregates in the synovium 1 and large bowel mucosa, 2 respectively. Such local development of lymphoid tissue is thought to contribute to the pathology of chronic inflammation. 3,4 Lymphoid tissue organization is orchestrated by a subset of the chemokine family, termed homeostatic or lymphoid chemokines because of their constitutive expression in secondary lymphoid tissues. 5 One of these lymphoid chemokines, CXCL13, also called B cell-attracting chemokine 1 (BCA-1) 6 or B-lymphocyte chemoattractant (BLC), 7 and its receptor CXCR5, also called Burkitt lymphoma receptor-1 (BLR1), are required for normal development of secondary lymphoid organs in mice. 8,9 CXCL13 and CXCR5 have, in addition, been detected in various chronic human inflammatory diseases where lymphoid neogenesis occurs, such as Helicobacter pylori gastritis, 10 RA, 1,11 Sjögren syndrome, 12-14 and UC 15 as well as in gastric 10 and primary central nervous system lymphoma. 16 Follicular dendritic cells (FDCs) are generally believed to be the main source of CXCL13 in normal 6,7,17 as well as inflamed lymphoid tissue. 1,10,11 In addition, vascular expression of the CXCL13 protein has been reported, 1,15,16,18,19 and CXCL13 and CXCR5 have been shown to play an important role in B-cell homing to murine Peyer patches. 20 However, no expression analysis of CXCL13 mRNA in human lymphoid tissue 10,15,16,18 has directly shown that CXCL13 is actually produced by FDCs or endothelial cells. Importantly, available data do not exclude the possibility that murine FDCs in fact bind CXCL13 rather than produce it. 7,17 Also of note, CXCL13 protein is undetectable in human FDC-like cells stimulated in vitro. 21 We have shown earlier that another lymphoid chemokine, CCL19, is present and functions in endothelial cells that are not its source. 22 In our recent human study of normal and aberrant gutassociated lymphoid tissue, we found that CXCL13 was mainly associated with extracellular fibrils and only minimally with cells displaying the traditional FDC phenotype. 15 This prompted us to explore more extensively the source of this chemokine in human lymphoid neogenesis represented by RA synovium and UC large bowel mucosa. Furthermore, we investigated the potential mechanistic role monocyte-derived cells could play in CXCL13 secretion. Our data documented for the first time that human monocytes/ macrophages are a potent inducible source of CXCL13 and, in fact, appear to be the main producers of this chemokine in inflammatory lesions where lymphoid neogenesis occurs. This suggested a role of recently extravasated macrophages in the formation of such ectopic follicles. Patients, materials, and methods PatientsClinicopathologic data and patient treatment schedules are provided in Table 1. Cryosections (8 m) were cut serially from various human tissue For personal use only. on May 10, 2018. by guest www.bloodjournal.o...

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Naive T cells are usually excluded from nonlymphoid tissues. Only when such tertiary tissues are subjected to chronic inflammation, such as in some (but not all) autoimmune diseases, are naive T cells recruited to these sites. We show that the CCR7 ligand CC chemokine ligand (CCL)21 is sufficient for attracting naive T cells into tertiary organs. We performed intravital microscopy of cremaster muscle venules in T-GFP mice, in which naive T cells express green fluorescent protein (GFP). GFP+ cells underwent selectin-dependent rolling, but no firm adherence (sticking). Superfusion with CCL21, but not CXC chemokine ligand 12, induced integrin-dependent sticking of GFP+ cells. Moreover, CCL21 rapidly elicited accumulation of naive T cells into sterile s.c. air pouches. Interestingly, a second CCR7 ligand, CCL19, triggered T cell sticking in cremaster muscle venules, but failed to induce extravasation in air pouches. Immunohistochemistry studies implicate ectopic expression of CCL21 as a mechanism for naive T cell traffic in human autoimmune diseases. Most blood vessels in tissue samples from patients with rheumatoid arthritis (85 ± 10%) and ulcerative colitis (66 ± 1%) expressed CCL21, and many perivascular CD45RA+ naive T cells were found in these tissues, but not in psoriasis, where CCL21+ vessels were rare (17 ± 1%). These results identify endothelial CCL21 expression as an important determinant for naive T cell migration to tertiary tissues, and suggest the CCL21/CCR7 pathway as a therapeutic target in diseases that are associated with naive T cell recruitment.

Ethical constraints restrict direct tracking of immune-cell migration throughout the human body in vivo. We, therefore, used deletion of the immunoglobulin M (IgM) heavy-chain constant-gene (C) segment as a marker to provide a dispersal signature of an effector B-cell subset (IgD ؉ IgM ؊ CD38 ؉ ) induced selectively in human tonsils. By DNA analysis, the C deletion identified dissemination of such blasts and their plasma-cell progeny to peripheral blood, lymph nodes, and bone marrow, as well as to mucosae and glands of the upper airways. Also the endocervix was often positive, while the small intestine was mainly negative, as could be expected from the identified homingmolecule profile of the marker cells, with relatively low levels of integrin ␣4␤7 and CC chemokine receptor 9 (CCR9). Of further importance for vaccine design, the circulating cells expressed abundantly CD62L (L-selectin) and CCR7, which provided a mechanism for integration of respiratory and systemic immunity. Most mucosal vaccines are at present administered perorally, and our results suggested that the nasal route is no alternative for vaccination against rotavirus or other small-intestinal infections in humans. However, immunization of nasopharynx-associated lymphoid tissue clearly appears preferable to target respiratory pathogens and may to some extent also protect against infections of the female genital tract. IntroductionMost pathogens use mucosae as portals of entry, and mucosal vaccines are therefore desirable, 1 particularly to elicit secretory IgA (SIgA) antibodies. 2,3 The secretory antibody system represents a major first-line defense and is triggered by antigens targeting mucosa-associated lymphoid tissue (MALT), which samples antigens directly from epithelial surfaces. 4 T and B cells activated in MALT home preferentially to mucosal effector sites, where B cells after extravasation undergo terminal differentiation. The local plasma-cell (PC) progeny cooperates with the polymeric Ig receptor (pIgR) to provide SIgA and secretory IgM (SIgM) antibodies. 5,6 Thus, locally produced IgA dimers and IgM pentamers are actively exported by the pIgR. For this epithelial transport mechanism to be operative, the Ig polymers depend on a selective structural incorporation of the J chain, 6,7 although the cytoplasmic expression of this peptide is a common characteristic of mucosal PCs regardless of their concurrent Ig isotype. 8,9 Induction of immunity at various mucosae is clearly an integrated response, but the traditional term "a common mucosal immune system" has detracted from the fact that there may be considerable compartmentalization. 4,5 This has been difficult to substantiate, however, because no inherent marker exists for mucosal B cells that unequivocally identify their MALT origin. Also notably, homing studies performed with primed human T cells, traced by 111 In labeling or gene marking, have provided conflicting results. 10,11 Nevertheless, rational site selection for mucosally applied vaccines would require detailed knowledge of w...

Secretory immunity is the best-defined part ot the mucosal immune system. This adaptive humoral defense mechanism depends on a fine-tuned cooperation between secretory epithelia and local plasma cells. Such mucosal immunocytes produce preferentially dimers and larger polymers of immunoglobulin A (collectively called pIgA), which contain J chain and therefore can bind to the epithelial secretory component (SC). This transmembrane glycoprotein functions as pIg receptor (pIgR) that also translocates pentameric IgM to the epithelial surface. B cells with a high level of J-chain expression and pIg-pIgR interactions at mucosal effector sites are thus necessary for the generation of secretory antibodies (SIgA and SIgM). Secretory antibodies perform immune exclusion in a first-line defense, thereby counteracting microbial colonization and mucosal penetration of soluble antigens. However, local production of pIgA is significantly down-regulated in inflammatory bowel disease (IBD), as revealed by strikingly decreased J-chain expression. Although the total increase of the immunocyte population in IBD lesions probably compensates for the relatively reduced pIgA production, decreased pIgR/SC expression in regenerating and dysplastic epithelium signifies that the SIgA system is topically deficient. There is, moreover, a significant shift from IgA2 to IgA1 production, the latter subclass being less resistant to proteolytic degradation. These changes--together with activation of mucosal macrophages and a dramatic increase of IgG-producing cells--may reflect local establishment of a second defense line which, however, is unsuccessful in its attempt to eliminate antigens derived from the indigenous microbial flora. Such a 'frustrated' local humoral immune system results in altered immunological homeostasis and jeopardized mucosal integrity. Complement activation observed in relation to epithelium-bound IgG1 in ulcerative colitis indicates, moreover, that the surface epithelium is subjected to immunological attack by an autoimmune reaction. These luminal deposits regularly contain terminal cytotoxic complement, and often also C3b as a sign of persistent activation. Comparison of identical twins, discordant with regard to ulcerative colitis, suggests that the markedly skewed local IgG1 response seen in this IBD entity may be genetically determined. The initial event(s) eliciting B-cell driven immunopathology in IBD remains unknown. Abrogation of oral tolerance to certain antigens from commensal bacteria has been suggested as a putative early mechanism, and lymphoid neogenesis and hyperplasia in the lesions most likely signify massive microbial overstimulation of the local B-cell system. Such ectopic lymphoid microcompartments may contribute substantially to the proinflammatory systemic-type of B-cell responses occurring in established IBD lesions.

SUMMARYWe compared B-cell phenotypes in Peyer's patches and solitary lymphoid follicles (organized gutassociated lymphoid tissue, GALT) with those in jejunal or ileal lamina propria. ) phenotypes occurred almost exclusively in GALT, whereas the lamina propria contained only scattered sIgA + CD27 + memory cells. In contrast, B-cell blasts and plasma cells negative for CD20 and often also for CD19 but with strong expression of CD38, CD27 and cytoplasmic IgA (cIgA), dominated in the lamina propria but were scarce in GALT. By¯ow cytometry, the proportion of dispersed CD19 + B lymphocytes varied from 4 to 42% among jejunal mucosal samples; between 5 and 50% of these were sIgD + , suggesting a variable contamination with GALT cells. B-cell blasts and plasma cells, identi®ed by their large size and strong expression of CD38, were regularly found (25±35% of the total mononuclear cell population). Distinction between B-cell blasts and mature plasma cells was made by the presence or absence of human leucocyte antigen (HLA) class II molecules, CD45RA, CD19 and surface immunoglobulin. No CD19 + B cells outside GALT expressed CD5, but a very small portion of the lamina propria B-cell blasts were positive for CD28. Dispersed sIgA + lamina propria cells expressed low levels of CD40, proliferated on CD40 ligation and constitutively secreted IgA in vitro. We concluded that the lamina propria B-cell compartment consists mainly of B-cell blasts and plasma cells but also has scattered, small sIgA + cells that can proliferate in response to CD40 ligation and may therefore function as local memory cells for recall antigens.

Laparoscopic adrenalectomy for metastases is feasible regardless of their sizes. However these procedures should be performed by highly skilled laparoscopic surgeon in a fully equipped operating room and with a coordinated operation team.