Differences in expression of gut-homing receptors on CD4+ T cells in black and white HIV-negative men who have sex with men.

HIV incidence rates are higher among black men who have sex with men (BMSM) as compared with MSM of other race/ethnicities in the USA. We found that blood memory CD4 cells from BMSM express higher levels of α4ß7, the gut-homing integrin, compared with white MSM. Higher expression of α4ß7 on blood CD4 cells correlated with higher percentage of proliferating CD4α4ß7 cells in rectal tissue suggesting increased trafficking of potential HIV target cells to rectal mucosa could increase HIV susceptibility among BMSM.

BATF is required for normal expression of gut-homing receptors by T helper cells in response to retinoic acid.

CCR9 and α4ß7 are the major trafficking receptors for lymphocyte migration to the gut, and their expression is induced during lymphocyte activation under the influence of retinoic acid (RA). We report here that BATF (basic leucine zipper transcription factor, ATF-like), an AP-1 protein family factor, is required for optimal expression of CCR9 and α4ß7 by T helper cells. BATF-deficient (knockout [KO]) mice had reduced numbers of effector T and regulatory T cells in the intestine. The intestinal T cells in BATF KO mice expressed CCR9 and α4ß7 at abnormally low levels compared with their wild-type (WT) counterparts, and BATF KO CD4(+) T cells failed to up-regulate the expression of CCR9 and α4ß7 to WT levels in response to RA. Defective binding of RARα and histone acetylation at the regulatory regions of the CCR9 and Itg-α4 genes were observed in BATF KO T cells. As a result, BATF KO effector and FoxP3(+) T cells failed to populate the intestine, and neither population functioned normally in the induction and regulation of colitis. Our results establish BATF as a cellular factor required for normal expression of CCR9 and α4ß7 and for the homeostasis and effector functions of T cell populations in the intestine.

Knockout of HIF-1α in tumor-associated macrophages enhances M2 polarization and attenuates their pro-angiogenic responses.

Tumor-associated macrophages (TAMs) constitute major infiltrates of solid tumors and express a marker profile that characterizes alternatively activated macrophages (MФs). TAMs accumulate in hypoxic tumor regions, express high amounts of hypoxia-inducible factor-1 (HIF-1) and contribute to tumor angiogenesis and invasiveness. However, the precise role of HIF-1 on MФ infiltration and phenotype alterations remains poorly defined. Therefore, we cocultured wild type (wt) versus HIF-1α(-/-) MФs with tumor spheroids. Both, wt and HIF-1α(-/-) MФs, infiltrated hypoxic regions of tumor spheroids at equal rates and got alternatively activated. Interestingly, significantly higher amounts of HIF-1α(-/-) MФs expressed the TAM markers CD206 and stabilin-1 compared with wt phagocytes. Stimulation of infiltrated TAMs with lipopolysaccharide (LPS)/interferon-γ revealed a reduced expression of the pro-inflammatory markers interleukin (IL)-6, tumor necrosis factor-α and inducible nitric oxide synthase in HIF-1α(-/-) MФs. Furthermore, HIF-1α(-/-) MФs were less cytotoxic toward tumor cells. Although infiltration of MФs increased the invasive potential of tumor spheroids independently of HIF-1, the ability to stimulate differentiation of stem cells toward CD31-positive cells was triggered by wt but not by HIF-1α(-/-) MФs. Our data suggest that HIF-1α-deficient MФs develop a more prominent TAM marker profile accompanied by reduced cytotoxicity, whereas HIF-1 seems indispensable for the angiogenesis-promoting properties of TAMs.

Alpha4(+)beta7(hi)CD4(+) memory T cells harbor most Th-17 cells and are preferentially infected during acute SIV infection.

Human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) infections are believed to infect minimally activated CD4(+) T cells after viral entry. Not much is known about why SIV selectively targets these cells. Here we show that CD4(+) T cells that express high levels of the alpha4beta7 heterodimer are preferentially infected very early during the course of SIV infection. At days 2-4 post infection, alpha4(+)beta7(hi)CD4(+) T cells had approximately 5x more SIV-gag DNA than beta7(-)CD4(+) T cells. alpha4(+)beta7(hi)CD4(+) T cells displayed a predominantly central memory (CD45RA(-)CD28(+)CCR7(+)) and a resting (CD25(-)CD69(-)HLA-DR(-)Ki-67(-)) phenotype. Although the expression of detectable CCR5 was variable on alpha4(+)beta7(hi) and beta7(-)CD4(+) T cells, both CCR5(+) and CCR5(-) subsets of alpha4(+)beta7(hi) and beta7(-)CD4(+) T cells were found to express sufficient levels of CCR5 mRNA, suggesting that both these subsets could be efficiently infected by SIV. In line with this, we found similar levels of SIV infection in beta7(-)CD4(+)CCR5(+) and beta7(-)CD4(+)CCR5(-) T cells. alpha4beta7(hi)CD4(+) T cells were found to harbor most T helper (Th)-17 cells that were significantly depleted during acute SIV infection. Taken together, our results show that resting memory alpha4(+)beta7(hi)CD4(+) T cells in the blood are preferentially infected and depleted during acute SIV infection, and the loss of these cells alters the balance between Th-17 and Th-1 responses, thereby contributing to disease pathogenesis.

Fucosyltransferase VII-positive, skin-homing T cells in the blood and skin lesions of atopic dermatitis patients.

Patients with atopic dermatitis (AD) have an abnormally increased frequency of cutaneous lymphocyte antigen (CLA)+ Th2 cells responsible for local inflammation; however, this is paradoxical, given the well-recognized defective capacity of Th2 cells to migrate to the skin sites of inflammation. These discrepant observations would stem from the ambiguity of CLA+ T cells, because CLA does not represent the epitope required for binding to E-selectin but the epitope generated by fucosyltransferase VII (Fuc-TVII) and because skin-homing T cells are composed of three distinct subpopulations; Fuc-TVII+ E-selectin ligand (ESL)+ CLA-, Fuc-TVII+ ESL+ CLA+ and Fuc-TVII- ESL- CLA+ cells. We therefore asked which subpopulations of skin-homing Th2 cells could be increased in the blood and skin lesions of AD. We analysed the frequencies of the three subpopulations in purified CD4+ peripheral blood T cells from AD patients and healthy controls by immunohistochemistry and flow cytometry. The Fuc-TVII+ CLA+ or CLA+ ESL+ CCR4+ cells were dramatically increased in frequency not only in the blood but also in the skin lesions of AD patients and this increase was related to the severity of the clinical symptoms. Our data indicate the clinical importance of identifying skin-homing T cells with the potent capacity to migrate into the skin by analysing their Fuc-TVII expression and E-selectin binding ability in patients with AD.

Role of tumor endothelium in CD4+ CD25+ regulatory T cell infiltration of human pancreatic carcinoma.

BACKGROUND: Regulatory T (Treg) cells have been detected in human carcinomas and may play a role in preventing the rejection of malignant cells. METHODS: We quantified Treg cells and the expression of the addressins and the respective ligands that attract them in blood and in human pancreatic tumors and adjacent nonmalignant tissues from 47 patients. The capacity of Treg cells to adhere to and transmigrate through autologous endothelial cells was tested in vitro using spheroid adhesion assays and in vivo using a xenotransplant NOD/SCID model and in the presence and absence of antibodies to addressins. All statistical tests were two-sided. RESULTS: More Treg cells infiltrated pancreatic carcinomas than adjacent nonmalignant pancreatic tissues (120 cells per mm2 versus 80 cells per mm2, difference = 40 cells per mm2, 95% confidence interval [CI] = 21.2 cells per mm2 to 52.1 cells per mm2; P<.001). In contrast to conventional CD4+ T cells, more blood-derived Treg cells adhered to (1.0% versus 5.2%, difference = 4.2%, 95% CI = 2.7% to 5.6%; P<.001) and transmigrated through (3332 cells versus 4976 cells, difference = 1644 cells, 95% CI = 708 cells to 2580 cells; P = .008) autologous tumor-derived endothelial cells in vitro and in vivo (458 cells versus 605 cells, difference = 147 cells, 95% CI = 50.8 to 237.2 cells; P = .04). Tumor-derived endothelial cells expressed higher levels of addressins--including mucosal adressin cell adhesion molecule-1 (MAdCAM-1), vascular cell adhesion molecule-1 (VCAM-1), CD62-E, and CD166--than endothelial cells from normal tissue. Experiments using antibodies to addressins showed that transmigration was mediated by interactions of addressins, including MAdCAM-1, VCAM-1, CD62-E, and CD166 with their respective ligands, beta7 integrin, CD62L, and CD166, which were expressed specifically on Treg cells. CONCLUSIONS: Tumor-induced expression of addressins on the surface of endothelial cells allows a selective transmigration of Treg cells from peripheral blood to tumor tissues.

Pathways of murine mast cell development and trafficking: tracking the roots and routes of the mast cell.

The appreciation of the role of the mast cell (MC) in inflammatory processes has expanded dramatically during the last decade. Many of these processes, especially more prolonged responses, are accompanied by an increase in the number of MCs, and much of this increase is likely because of recruitment of immature progenitors with subsequent maturation under the control of the tissue microenvironment. We have begun to identify many of the cell-surface molecules that control this influx and have traced the development of these cells back to their hematopoietic roots. This development proceeds along the myelomonocytic pathway with distinct intermediates having been identified in both bone marrow and spleen. The expression of alpha4beta7 integrins has played a prominent role in this process, as it helped identify a bipotent basophil MC precursor in the spleens of C57BL/6 mice. This integrin also controls basal influx into the intestine and, along with alpha4beta1 integrins, plays a critical role in recruitment to inflamed lungs. Investigation of chemokines and chemokine receptors in these processes led to the identification of a dual role for the murine interleukin-8 receptor CXCR2. This alpha-chemokine receptor affects MC progenitor trafficking by its expression by MC progenitors and by its expression on stromal cells, likely endothelium, affecting trafficking to both intestine under basal conditions and lung during inflammatory recruitment.

T-cell distribution and adhesion receptor expression in metastatic melanoma.

PURPOSE: Metastatic malignant melanoma is a devastating disease with a poor prognosis. Recent therapeutic trials have focused on immunotherapy to induce development of endogenous antitumor immune responses. To date, such protocols have shown success in activation of tumor-specific CTL but no overall improvement in survival. To kill tumor, antigen-specific CTL must efficiently target and enter tumor tissue. The purpose of this study was to examine the pathway of leukocyte migration to metastatic melanoma. EXPERIMENTAL DESIGN: Peripheral blood and metastatic melanoma tissues (n = 65) were evaluated for expression of adhesion molecules using immunohistochemistry of tumor sections and flow cytometry of tumor-associated and peripheral blood CTL and compared with healthy controls. CTL expressing T-cell receptors for the melanoma antigen MART-1 were identified in a subset of samples by reactivity with HLA-A2 tetramers loaded with MART-1 peptide. RESULTS: Results show that the majority of metastatic melanoma samples examined do not express the vascular adhesion receptors E-selectin (CD62E), P-selectin (CD62P), and intercellular adhesion molecule-1 (CD54) on vessels within the tumor boundaries. Strong adhesion receptor expression was noted on vessels within adjacent tissue. Tumor-associated T lymphocytes accumulate preferentially in these adjacent areas and are not enriched for skin- or lymph node-homing receptor phenotype. CONCLUSION: Expression of leukocyte homing receptors is dysregulated on the vasculature of metastatic melanoma. This results in a block to recruitment of activated tumor-specific CTL to melanoma metastases and is a likely factor limiting the effectiveness of current immunotherapy protocols.

The role of skin-homing T cells in extrinsic atopic dermatitis.

BACKGROUND: T cells that express Cutaneous Lymphocyte-Associated antigen (CLA) have the potential of migrating to the skin, and are hypothesized to play a role in cutaneous atopic disease. AIM: To investigate the immune phenotype and cytokine responses to Der p 1 stimulation of CLA+ T cells in extrinsic atopic dermatitis (EAD). DESIGN: In vitro testing, with controls. METHODS: Peripheral blood mononuclear cells (PBMC) were obtained from EAD patients (n=27) and non-atopic healthy individuals (n=22). Phenotypic analysis of naive, CLA+ and non-CLA+ memory/effector CD4+ and CD8+ T cells used markers of cell activation, differentiation, adhesion, apoptosis and chemokine receptor expression. Cytokine responses in these cells were studied following Der p 1 stimulation. RESULTS: CLA+ T cells from EAD patients expressed significantly higher levels of CD25, HLA-DR, CD38, CD71, CXCR1, CXCR2 and lower levels of bcl2, CCR5, CCR7, CXCR3, and CD62L (p<0.05). DISCUSSION: In EAD patients, CLA+ T cells express increased levels of markers associated with activation, adhesion and apoptosis, show differences in the level of expression of differentiation markers and display a distinct chemokine receptor preference, compared with cells from healthy controls. These data suggest a significant role for CLA+ T cells in the pathogenesis of cutaneous atopic disease.

Cytokine production, activation marker, and skin homing receptor in children with atopic dermatitis and bronchial asthma.

T cells are known to develop a critical role in the pathogenesis of atopic dermatitis (AD) and bronchial asthma. T cells involved in AD express the skin homing receptor CLA, but no lung homing receptor has been identified in bronchial asthma. We compared different cell markers and the cytokine production in T cells from children with AD or bronchial asthma. We studied the involvement of CLA+ and CLA- T-cell subpopulations in these diseases. We studied 20 children with acute AD lesions, 15 with mild persistent asthma, and 15 non-atopic controls. All patients were sensitized to house dust mite (DP) and evaluated during the acute phase. Total and specific IgE were measured by immunoassay and the expression of different cell markers and the cytokine production was analyzed by flow cytometry in peripheral blood mononuclear cells. Total IgE was significantly higher in AD children and IgE to DP in the asthmatic children. There was a significant increase in CD25+ CD4+ cells in asthmatic children and in HLA-DR+ CD4+ and HLA-DR+ CD8+ cells in AD. In the CD4+ subsets, there was an increase in IL-13, IL-5 and TNF-alpha in AD compared to controls, a decrease in IFN-gamma in asthmatic children compared to controls, and an increase in IL-13, IL5, IL2, TNF-alpha, and IFN-gamma in the AD compared to asthmatic children. Changes in cytokine production were mainly detected in CLA+ cells in AD and in CLA- cells in asthma. Differences exist in total and specific IgE, activation markers, and cytokine patterns between AD children and children with asthma, with the former expressing a Th2 pattern whereas in asthmatic children we only detected a decrease in IFN-gamma. Moreover, the subpopulations (CLA+ vs. CLA-) expressing these changes were different, indicating that the underlying mechanisms in the two diseases are not exactly the same.

Expression of cutaneous lymphocyte-associated antigen and E-selectin ligand by circulating human memory CD4+ T lymphocytes specific for herpes simplex virus type 2.

Virus-specific memory T lymphocytes traffic to sites of viral infection. Herpes simplex virus (HSV) type 2-specific CD4(+) and CD8(+) T lymphocytes differ with regard to their homing kinetics to infected tissues. We studied the expression of cutaneous lymphocyte-associated antigen (CLA) and E-selectin ligand (ESL) by HSV-2-specific CD4(+) T lymphocytes. Virus-reactive T lymphocytes were identified ex vivo by CD154 or interferon-gamma up-regulation. We detected selective expression of CLA by HSV-2-reactive CD4(+) T lymphocytes, but at levels lower than those we previously observed for CD8(+) T lymphocytes. Short-term HSV-2-reactive CD4(+) lines generated from peripheral-blood mononuclear cells preferentially express CLA, compared with cytomegalovirus- or influenza-specific cells. CLA is expressed by HSV-2-reactive cells that are initially CLA negative before restimulation. Short-term culture-expanded HSV-2-specific CD4(+) T lymphocytes also selectively express ESL. These findings have implications for the optimization of vaccines for HSV and other cutaneous pathogens.

Semiquantative analysis of expression of mucosal addressin cell adhesion molecule-1 during small bowel graft rejection in rats.

AIM: Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) mediates the homing of lymphocytes to gut-associated lymphoid tissues (GALT). We performed a semiquantative analysis of MAdCAM-1 expression during small bowel graft rejection. METHODS: Orthotopic small bowel transplantations (SBT) were performed from BN rats to LEW rats. Isografted animals served as controls. Animals were sacrificed on days 3, 4, 5, 6, and 7 after SBT. Cryostat sections were prepared from grafts, including Peyer's patches (PPs). Indirect immunoperoxidase staining was performed using mAbs against MAdCAM-1. The degree of vascular endothelial staining on high endothelial venules (HEV) in the PPs was graded from 1 (low levels) to 5 (high levels), and in the vessels of the lamina propria from 1 (faint), 2 (low at the base of villi), 3 (low to the middle of villi), 4 (high to the middle of villi), to 5 (high to villus tip). RESULTS: MAdCAM-1 expression on HEVs in PPs was down-regulated during rejection. In contrast its expression on endothelial cells of vessels in the lamina propria was up-regulated during rejection. CONCLUSION: Alteration in MAdCAM-1 expression may be associated with the development of SB graft rejection. The vessels at the base of villi, which are associated with lymphocyte recruitment, may become sites of intense immune reactivity during the early phase of small bowel allograft rejection.

Possible link between unique chemokine and homing receptor expression at diagnosis and relapse location in a patient with childhood T-ALL.

Childhood acute lymphoblastic leukemia (ALL) is often associated with extramedullary infiltration by leukemic cells at diagnosis or at relapse. To understand the mechanisms behind the dissemination of T-cell ALL (T-ALL) cells this study investigated the homing receptor expression on the blast cells of 11 pediatric T-ALL patients at diagnosis. One patient revealed a unique profile with high expression of the chemokine receptor CCR9 and the integrin CD103 on the T-ALL cells. Both of these molecules are specifically associated with homing to the gut. This finding was clinically significant as the patient later suffered a relapse that was confined to the gut. Immunohistochemistry revealed that the leukemic cells in the gut still expressed CCR9 and colocalized with a high expression of the CCR9 ligand, CCL25. These findings suggest that the original expression of CCR9 and CD103 on the leukemic cells contributed to the relapse location in the gut of this patient.

Cutaneous lymphocyte antigen expression on human effector B cells depends on the site and on the nature of antigen encounter.

In contrast to T cells, information on skin-homing B cells expressing the cutaneous lymphocyte antigen (CLA) is sparse. CLA expression on human B cells was investigated among circulating immunoglobulin-secreting cells (ISC) and among antigen-specific antibody-secreting cells (ASC) elicited by parenteral, oral or rectal primary immunization, or by parenteral or oral secondary immunization with Salmonella typhi Ty21a. CLA expression was examined by combining cell sorting with an enzyme-linked immunospot assay. Among all ISC, the proportion of CLA(+) cells was 13-21%. Parenteral immunization induced antigen-specific ASC of which 13% were CLA(+), while oral and rectal immunizations were followed by only 1% of CLA(+) ASC (p<0.001). Oral re-immunization was followed by an up-regulation of CLA (34-48%) regardless of the route of priming. Parenteral re-immunization elicited ASC of which 9-14% were CLA(+). In conclusion, the expression of CLA on human effector B cells depends on the site of antigen encounter: intestinal stimulation elicits cells with no CLA, while parenteral encounter elicits significant numbers of CLA(+) cells. Even though primary antigen encounter in the intestine failed to stimulate CLA expression, up-regulation of CLA was found upon intestinal antigen re-encounter. These findings may be of relevance in the pathogenesis of some cutaneous disorders.

The systemic immune response is more prominent than the mucosal immune response in the pathogenesis of periodontal disease.

BACKGROUND/AIM: The diseased periodontium appears to express features of a systemic and a mucosal immune response. Our aims were to determine differences in immunoglobulin expression between gingivitis and periodontitis lesions and to ascertain whether immune and inflammatory cells were recruited into the diseased periodontium by the mucosal addressin adhesion molecule (MAdCAM-1). METHODS: In situ hybridization and immunohistochemistry were used to detect the expression of chemokines, adhesion molecules and immunoglobulins in tissue sections of gingival and granulation tissues excised from periodontitis-affected sites and of healthy tissue and gingivitis-affected tissue excised during crown-lengthening procedures. RESULTS: Greater numbers of plasma cells were observed in periodontitis gingival/granulation tissue lesions compared with gingivitis lesions. While IgA1 were predominant in all lesions, IgA2 and J-chain expressing plasma cells were present in increased proportions in gingival tissues compared with granulation tissue. Intracellular adhesion molecule-1 (ICAM-1) was higher in periodontitis than in gingivitis and interleukin-8 mRNA was higher in lesions with a pronounced neutrophil infiltrate. Vascular cell adhesion molecule-1 (VCAM-1) localized to the deep connective tissue and indicated the presence of a systemic type of immune response in this region. Periodontal tissues (n=71 biopsies) did not appear to express MAdCAM-1, in positive control sections of small intestine where it was detected. CONCLUSION: Overall, the systemic-type immune response is predominant, and although the mucosal immune response is minor and limited to the superficial tissues it may have an important role in the host defense to periodontal pathogens.

Long-term alterations of oral mucosa in radiotherapy patients.

PURPOSE: The aim of this investigation was to describe the alterations in oral mucosa after radiotherapy. METHODS AND MATERIALS: Biopsies were taken from patients before irradiation, at 60 Gy, and 6-12 months after radiotherapy. Histomorphological evaluation of the vessels was performed, and endothelial expression of ICAM-1, VCAM-1, and E-selectin was also evaluated, as well as distribution of LFA-1-, Mac-1-, VLA-4-, RM3/1-, 27E10-, and 25F9-bearing cells in the subepithelial tissue. RESULTS: The expression of ICAM-1 was downregulated after radiotherapy, whereas the percentage of LFA-1- and VLA-4-bearing cells increased. VCAM-1 remained at low levels. The subepithelial infiltration was still dominated by RM3/1-positive macrophages. The number of vessels decreased, while the lumina of the remaining vessels in the deeper connective layer increased. CONCLUSIONS: The late effects of radiotherapy are characterized by a decreased number of blood vessels and by significantly different expression patterns of the adhesion molecules studied, and of integrins and macrophage subpopulations compared to the conditions before irradiation and at 60 Gy.

Analysis of the expression of cutaneous lymphocyte-associated antigen on the peripheral blood and cutaneous lymphocytes of alopecia areata patients.

Alopecia areata has been reported to be accompanied by abnormal autoimmune dysfunction. We examined the expression of cutaneous lymphocyte-associated antigen (CLA), which is a skin-specific lymphocyte homing receptor, in the peripheral blood lymphocytes and skin of patients with alopecia areata. In the patients' peripheral blood, the percentage of CLA-positive CD4+ or CD8+ lymphocytes, was significantly higher than that of normal controls. The patients with severe or progressive alopecia areata showed a much higher CLA-positivity compared to patients recovering from the disease. A chronological study showed that the percentage of CLA-positive peripheral blood lymphocytes, CD4 + or CD8 + lymphocytes decreased in parallel with the patients' good clinical course. The CLA-positivity in peripheral blood lymphocytes, CD4+ or CD8+ lymphocytes of patients with alopecia areata who did not respond to oral corticosteroid therapy remained higher than in those who responded well to the treatment. In the affected scalp skin, many infiltrating lymphocytes around the hair follicles, which were CD4+ or CD8+ lymphocytes, expressed CLA. These findings suggest that the CLA-positivity correlates with clinical activity and that CLA-positive CD4+ or CD8+ lymphocytes may play an important role in alopecia areata.

Trafficking machinery of NKT cells: shared and differential chemokine receptor expression among V alpha 24(+)V beta 11(+) NKT cell subsets with distinct cytokine-producing capacity.

Natural killer T (NKT) cells are important regulators of the immune system, but their trafficking machinery, including expression of chemokine receptors, has been poorly defined. Unlike other conventional T-cell populations, we show that most NKT cells express receptors for extralymphoid tissue or inflammation-related chemokines (CCR2, CCR5, and CXCR3), while few NKT cells express lymphoid tissue-homing chemokine receptors (CCR7 and CXCR5). A population with homing potential for lymph nodes (L selectin(+) CCR7(+)) exists only within a small subset of CD4 NKT cells. We show differential expression of chemokine receptors among NKT cell subsets: CCR4 is mainly expressed by a high cytokine (interleukin-4/interleukin-2)-producing (CD4) NKT subset, while CCR1, CCR6, and CXCR6 are preferentially expressed by the low cytokine-producing CD8 and CD4(-)CD8(-) subsets. In line with this, TARC/CCL17 (a CCR4 ligand) induces preferential chemotaxis of the CD4 NKT subset, while chemotactic activities of LARC/CCL20 (a CCR6 ligand) and MIP-1 alpha/CCL3 (a CCR1 ligand) are focused on the CD8 and CD4(-)CD8(-) NKT cells. We conclude that, unlike conventional naive, memory, or effector T cells, the entire NKT cell population expresses nonlymphoid tissue homing chemokine receptors, yet NKT cell subsets differ considerably from each other by displaying distinct and reciprocal expression patterns of some chemokine receptors. Our results identify chemokine receptors that are potentially important for trafficking of human blood NKT cell subsets and reveal their function (cytokine production capacity)-dependent differential trafficking potentials.

Functionally distinct subsets of CD1d-restricted natural killer T cells revealed by CD1d tetramer staining.

CD1d-restricted natural killer (NK)T cells are known to potently secrete T helper (Th)1 and Th2 cytokines and to mediate cytolysis, but it is unclear how these contrasting functional activities are regulated. Using lipid antigen-loaded CD1d tetramers, we have distinguished two subsets of CD1d-restricted T cells in fresh peripheral blood that differ in cytokine production and cytotoxic activation. One subset, which was CD4(-), selectively produced the Th1 cytokines interferon gamma and tumor necrosis factor alpha, and expressed NKG2d, a marker associated with cytolysis of microbially infected and neoplastic cells. This subset up-regulated perforin after exposure to interleukin (IL)-2 or IL-12. In contrast, CD4(+) CD1d-restricted NKT cells potently produced both Th1 and Th2 cytokines, up-regulated perforin in response to stimulation by phorbol myristate acetate and ionomycin but not IL-2 or IL-12, and could be induced to express CD95L. Further, for both CD1d-restricted NKT cell subsets, we found that antigenic stimulation induced cytokine production but not perforin expression, whereas exposure to inflammatory factors enhanced perforin expression but did not stimulate cytokine production. These results show that the various activities of CD1d-restricted T cells in tumor rejection, autoimmune disease, and microbial infections could result from activation of functionally distinct subsets, and that inflammatory and antigenic stimuli may influence different effector functions.

Fetal haemopoietic cells display enhanced migration across endothelium.

Fetal haemopoietic cells continually circulate and migrate into tissues, and thus may have specialized homing capabilities. In this study we investigated the in vitro features of haemopoietic cells in fetal blood and liver which are relevant to homing and engraftment. Fetal cells were examined for long-term culture-initiating cell (LTC-IC) and progenitor content, adhesion molecule expression, cell cycle behaviour and transendothelial migratory activity. The LTC-IC content of fetal CD34+ cells is similar to that of CD34+ cells from cord and adult mobilized blood. In contrast to adult and cord blood CD34+ cells, fetal CD34+ cells were actively cycling (11.0 +/- 1.7% and 28 +/- 1.1% of fetal blood and liver CD34+ cells, respectively, in S+G2M, P < 0.001, compared with cord and adult cells). The striking finding was that fetal haemopoietic cells (both LTC-ICs and committed progenitors) displayed significantly higher levels of migration across endothelium (P < 0.05 compared with cord, P < 0.01 compared with adult blood and bone marrow CD34+ cells), which were further increased by chemokines and growth factors. The superior migratory activity of fetal haemopoietic cells may underlie a more efficient homing ability, in keeping with their physiological role.