CD8alpha Expression Research Articles

Recently alloactivated CD4+CD8−CD25+T regulatory cells express CD8alpha and are potent suppressor cells

Abstract Therapy with antigen-specific CD4+CD25+ T regulatory cells (Treg) for induction of transplant tolerance is desirable, as naïve thymic Treg (tTreg) are non-antigen specific and weak suppressor cells. Naïve tTreg from DA rats cultured with fully allogeneic PVG stimulator cells and IL-2 express IFN-gamma receptor (IFNGR) and IL-12 receptor beta2 (IL-12Rb2) and are more potent alloantigen-specific regulators that we call Ts1 cells. This study examined other markers that could identify the activated alloantigen-specific Treg as a subpopulation within the CD4+CD25+Foxp3+Treg. After culture of naïve DA CD4+CD8−CD25+T cells with rIL-2 and PVG alloantigen, CD8a was expressed on 10–20% and CD8b on <5% of these cells. RT-PCR showed the CD8+ cells had increased Ifngr that characterizes Ts1 cells as well was Irf4, a transcription factor induced by TCR activation. Proliferation induced by re-culture with rIL-12 and alloantigen was greater with CD4+CD8+CD25+Treg consistent with the CD8a+ cells expressing IL-12R. In MLC, the CD8+ fraction had greater suppression than the mixed Ts1 population, whereas the CD4+CD8−CD25+T cells had less suppression. In an adoptive transfer assay, rIL-2 and alloantigen activated Treg suppress rejection at a ratio of 1:10 with naïve effector cells, whereas alloantigen and rIL-2 activated tTreg depleted of the CD8a cells did not prevent rejection. This study showed the expression of CD8alpha by rIL-2 and alloantigen activation of CD4+CD8−CD25+Foxp3+T cells was a marker of alloantigen-specific Treg and may be of use to enrich alloantigen-specific Treg.

Mucosal Gamma/Delta T Cells Increased by i.n. Administration of Gliadin to Four-Week-Old NOD Mice Prevent Diabetes in the NOD-SCID Model of Adoptive Cotransfer of Diabetes

Beta-cell autoantigens, e.g., insulin, proinsulin, or GAD65, have been investigated both in animal models and human trials for induction of beta-cell specific tolerance to prevent the development of type 1 diabetes (T1D). On the other hand, environmental factors that significantly contribute to the recent outbreak of T1D were less studied, probably due to their complexity. The dietary wheat protein fraction has been associated with high penetrance of the disease, whereas gluten-free diets prevented T1D in animal models. We have previously reported that i.n. administration of gliadin prevented diabetes in NOD mice. Herewith we investigated mucosal gamma/delta T cells that were induced by i.n. administration of gliadin for their regulatory capacity to prevent diabetes in the NOD-SCID model of diabetes co-transfer. I.n. administration of gliadin to 4-week-old NOD mice increased proportion of gamma/delta T cells in pancreatic and mesenteric lymph nodes. Adoptive co-transfer of 2x106 gamma/delta T cells with 1x107 diabetogenic splenocytes led to statistically significant (p<0.01) diabetes prevention. The gamma/delta T cells were characterized for their memory-naïve and mucosal homing properties, or NK-like features by assessing expression of CD8alpha, CD45RB, CD62L, CCR7, CD103 and NKG2D by flowcytometry. In conclusion, similar to i.n. administration of insulin, i.n. vaccination with gliadin, an environmental antigen with possible ethiological influence in T1D, led to increased proportion of mucosal gamma/delta T cells. These gamma/delta T cells possess regulatory capacity to prevent diabetes transfer in the NOD-SCID model and may represent a novel and safer strategy for prevention or an early intervention in T1D. Disclosure D. Funda: None. J. Golias: None. M. Haupt-Jorgensen: None. K. Buschard: None.

Abstract 904: Lifetime genistein alters mammary tumors’ response to anti-estrogen tamoxifen treatment by affecting immune function in rats

Abstract Consistent with the human data showing that soy intake reduces the risk of breast cancer recurrence, we have previously reported that childhood and lifelong genistein (GEN) intake enhanced response of mammary tumors to tamoxifen (TAM) treatment and prevented recurrence in rats. Mammary tumor recurrence was also inhibited by starting GEN consumption in adulthood. Since GEN is shown to alter immune functions, and tumor immune responses can determine cancer outcome, we examined several immune markers in the tumor prior to TAM treatment. Female Sprague-Dawley rats were fed control AIN93G diet or AIN93G diet supplemented with 500 ppm GEN either during childhood (between postnatal days 15 and 30), adulthood (from 55 days to end of the study), or both. Mammary tumors were induced by DMBA at the age of 48 days, and when a tumor reached a size of 1.4 cm in diameter (criteria for starting TAM treatment in the previous study), rats were euthanized (n = 15 per group), and blood and mammary tumors were collected. We determined the expression of CD8-alpha (present in cytotoxic T lymphocytes) and Foxp3, TGFβ1 and TGF2 (present in regulatory T-cells, Treg) in mammary tumors from rats with varying lifetime exposures to GEN. Compared with the control rats, expression of CD8-alpha mRNA was significantly increased by GEN intake at any time during the life cycle, suggesting an elevation in cytotoxic T-cells density infiltrating the tumor. Foxp3 and TGF-β1 mRNA were significantly reduced by GEN consumption. Increased Treg levels in tumors result in the suppression of immune responses; therefore, a reduction in Foxp3 and TGF-β1 may indicate a decrease in immune suppression. TGF-2 mRNA expression was significantly increased in the tumors of rats that consumed GEN only as adults. In the serum, interleukin (IL)-1 and IL-6 levels were significantly elevated in rats that consumed GEN only during childhood, whilst IL-6 was reduced in rats consuming GEN during lifetime or only as adults. IL-12 that is reported to stimulate cellular immunity, was increased in the rats that consumed GEN during lifetime or as adults. Our findings suggest that the ability of GEN intake to prevent mammary cancer recurrence is associated with improved immune responses in the tumor. Citation Format: Xiyuan Zhang, Katherine Cook, Leena Hilakivi-Clarke. Lifetime genistein alters mammary tumors’ response to anti-estrogen tamoxifen treatment by affecting immune function in rats. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 904. doi:10.1158/1538-7445.AM2015-904

High dose antigen stimulation leads to binding defects caused by persistent spatial segregation of TCR and CD8 in cytotoxic T cells (178.9)

Abstract The lateral organization of surface receptors controls ligand binding and activation. Our group has shown that activated T Cells exhibit persistent clustering of T Cell Receptor (TCR) several days after stimulation, leading to enhanced binding of soluble Major Histocompatibility Complex (MHC) dimers at low concentrations. In contrast, other groups have shown a complete loss of binding in activated T Cells during the same time period. Here, we resolve this contradiction by demonstrating that persistent binding behavior is controlled by the dose of antigen during primary activation. T Cells from TCR transgenic mice stimulated with high but not low dose of peptide are unable to specifically bind soluble Kb-SIY or Db-GP100 MHC dimer four days after stimulation. The behavior is not due to differences in the surface expression of TCR, CD8alpha, or CD8beta. Cytokine production mirrors the loss of binding. However, both high and low dose stimulated cells are able to bind the so-called ‘CD8 independent’ Ld-QL9 dimer, implicating the coreceptor in the binding defect. Using biophysical binding assays, k-space Image Correlation Spectroscopy, and Forster Resonance Energy Transfer between TCR and CD8, we demonstrate that TCR and CD8 are segregated, and TCR unclustered, on high dose activated T Cells, impairing CD8-dependent binding. Thus, membrane organization derived binding defects represent a mechanism for controlling T Cell responses to supraoptimal antigen.

The CD8+ dendritic cell subset

Mouse lymphoid tissues contain a subset of dendritic cells (DCs) expressing CD8 alpha together with a pattern of other surface molecules that distinguishes them from other DCs. These molecules include particular Toll-like receptor and C-type lectin pattern recognition receptors. A similar DC subset, although lacking CD8 expression, exists in humans. The mouse CD8(+) DCs are non-migrating resident DCs derived from a precursor, distinct from monocytes, that continuously seeds the lymphoid organs from bone marrow. They differ in several key functions from their CD8(-) DC neighbors. They efficiently cross-present exogenous cell-bound and soluble antigens on major histocompatibility complex class I. On activation, they are major producers of interleukin-12 and stimulate inflammatory responses. In steady state, they have immune regulatory properties and help maintain tolerance to self-tissues. During infection with intracellular pathogens, they become major presenters of pathogen antigens, promoting CD8(+) T-cell responses to the invading pathogens. Targeting vaccine antigens to the CD8(+) DCs has proved an effective way to induce cytotoxic T lymphocytes and antibody responses.

Identification of three distinct subsets of migrating dendritic cells from oral mucosa within the regional lymph nodes

To investigate the phenotypic and migrational properties of oral mucosal dendritic cells (OMDCs), fluorescein isothiocyanate (FITC) was painted onto mouse buccal mucosa and the expression patterns of functional molecules in FITC-bearing migrating DCs within the regional lymph nodes (RLNs) were analysed. We found three distinct subpopulations of migrating OMDCs within the RLNs: CD11c(hi) CD207(-) (F1), CD11c(int/lo) CD207(-) (F2) and CD11c(int/lo) CD207(+) (F3). The F1 DCs reached the RLNs earlier (after 24 hr) but diminished immediately. Additionally, F1 DCs expressed high levels of CD11b. The F2 DCs migrated continuously to the RLNs and maintained the highest ratio of all three fractions. The F3 DCs migrated slowly to the RLNs and demonstrated a late peak at 96 hr. In addition, F3 DCs showed the highest CD205 expression levels of all three subsets. All fractions of migrating OMDCs expressed CD80, CD86 and major histocompatibility complex class II at high levels, suggesting that all OMDCs are in a mature stage and have the potential for antigen presentation. All migrating OMDCs lacked CD8alpha expression. Taken together, our results indicate that the lack of CD207 is one factor that identifies submucosal DCs. Both F1 and F2 DCs lack CD207; F1 DCs are resident and F2 DCs are newly recruited following FITC application. The F3 DCs, which express CD207, are mucosal Langerhans cells that migrate later. The identification of OMDC subsets should facilitate further studies investigating the functional roles of each fraction.

Spondylarthritis in HLA–B27/human β2‐microglobulin–transgenic rats is not prevented by lack of CD8

HLA-B27 predisposes to spondylarthritis by an unknown mechanism. A logical candidate mechanism is through recognition of B27 by CD8+ T cells. The purpose of this study was to examine the effects of a lack of CD8 on the spondylarthritis that develops in B27/human beta(2)-microglobulin (Hubeta(2)m)-transgenic rats. A missense mutation in the CD8a gene that causes a loss of CD8alpha expression was identified in offspring of a male Sprague-Dawley rat that had been treated with the mutagen N-ethyl-N-nitrosourea. The mutation was crossed into B27/Hubeta(2)m-transgenic lines on the Lewis background. CD8a(-/-) and CD8a(+/-) progeny were compared on a mixed SD-LEW background as well as after at least 10 backcrosses to LEW rats. CD8 function was assessed by generating cytolytic T lymphocytes (CTLs) against allogeneic DA strain antigens. Homozygous mutant rats showed normal CD8a and CD8b messenger RNA levels but no detectable expression of either protein and an almost complete abrogation of the allogeneic CTL response. Two disease phenotypes previously observed in different B27/Hubeta(2)m-transgenic lines also occurred in the respective CD8a(-/-)-transgenic rat lines. There was no significant difference in disease prevalence or severity between CD8a(-/-) rats and CD8a(+/-) rats. All of the previously described disease manifestations in HLA-B27/Hubeta(2)m-transgenic rats arise in the absence of any functional CD8+ T cells. It thus seems unlikely that classic T cell recognition of HLA-B27 is of primary importance in this animal model. The possibility of a secondary role of a CD8-dependent mechanism cannot be entirely excluded.

Differential Expression of Immune Genes in Atlantic Salmon (Salmo salar L.) Challenged Intraperitoneally or by Cohabitation with IPNV

Atlantic salmon smolts challenged intraperitoneally (ip) and by cohabitation with a highly virulent strain of infectious pancreatic necrosis virus showed strong activation of important immune genes in spleen, liver, head-kidney and gill measured by real-time quantitative PCR. The genes investigated were IL-1beta, IL-10, IFN-alpha, IFN-gamma, Mx, MHC-I, MHC-II, TCR-alpha, CD8-alpha and mIgM. A low final cumulative mortality of about 10% was seen in the ip-challenged group, while more than 40% of the cohabitants died in the sampling period. Sampling was performed at day 15, 24 and 37 post ip-challenge. Overall, the expression of the investigated genes varied highly. The expression of IL-1beta, IL-10, MHC-II, TCR-alpha, CD8-alpha and mIgM showed more or less the same patterns between the two groups of fish by being significantly upregulated at day 24 post ip-challenge. However, the degree of regulation varied a lot among the genes. A pattern showing differences between ip-challenged and cohabitants were seen for IFN-gamma and especially IFN-alpha, where the upregulation seemed to last longer for the cohabitants. The Mx gene was the most induced gene, but also the one with highest individual variance. Mx but also MHC-I were both still highly upregulated at the last sampling point within both groups of fish. The results seem to indicate that the differences in expression pattern(s) could reflect the different routes of entrance of the virus into the fish. This could maybe explain the different kinetics in the onset and the degree of mortality or the potential different molecular mechanisms used for combating the virus.

The T-box transcription factor eomesodermin controls CD8 T cell activity and lymph node metastasis in human colorectal cancer

Background/aims:An efficient cytolytic T cell function is essential for immune mediated rejection of colorectal cancer. However, the molecular mechanisms driving T cell mediated cancer rejection are still poorly understood. Here,...

Dose‐dependent modulation of CD8 and functional avidity as a result of peptide encounter

The generation of an optimal CD8(+) cytotoxic T lymphocyte (CTL) response is critical for the clearance of many intracellular pathogens. Previous studies suggest that one contributor to an optimal immune response is the presence of CD8(+) cells exhibiting high functional avidity. In this regard, CD8 expression has been shown to contribute to peptide sensitivity. Here, we investigated the ability of naive splenocytes to modulate CD8 expression according to the concentration of stimulatory peptide antigen. Our results showed that the level of CD8 expressed was inversely correlated with the amount of peptide used for the primary stimulation, with higher concentrations of antigen resulting in lower expression of both CD8alpha and CD8beta. Importantly the ensuing CD8(low) and CD8(high) CTL populations were not the result of the selective outgrowth of naive CD8(+) T-cell subpopulations expressing distinct levels of CD8. Subsequent encounter with peptide antigen resulted in continued modulation of both the absolute level and the isoform of CD8 expressed and in the functional avidity of the responding cells. We propose that CD8 cell surface expression is not a static property, but can be modulated to 'fine tune' the sensitivity of responding CTL to a defined concentration of antigen.

Curriculum vitae of intestinal intraepithelial T cells: their developmental and behavioral characteristics

The alimentary tract has an epithelial layer, consisting mainly of intestinal epithelial cells (IECs), that is exposed to the exterior world through the intestinal lumen. The IEC layer contains many intestinal intraepithelial T cells (IELs), and the total number of IELs constitutes the largest population in the peripheral T-cell pool. Virtually all gammadelta-IELs and many alphabeta-IELs in the mouse small intestine are known to express CD8 alpha alpha homodimers. A wide range of evidence that supports extrathymic development of these CD8 alpha alpha(+) IELs has been collected. In addition, while several studies identified cells with precursor T-cell phenotypes within the gut epithelium, how these precursors, which are dispersed along the length of the intestine, develop into gammadelta-IELs and/or alphabeta-IELs has not been clarified. The identification of lymphoid cell aggregations named 'cryptopatches' (CPs) in the intestinal crypt lamina propria of mice as sites rich in T-cell precursors in 1996 by our research group, however, provided evidence for a central site, whereby precursor IELs could give rise to T-cell receptor-bearing IELs. In this review, we discuss the development of IELs in the intestinal mucosa and examine the possibility that CPs serve as a production site of extrathymic IELs.

Th1/Th2 xenogenic antibody responses are associated with recipient dendritic cells

We characterized dendritic cells (DC) phenotypically and functionally between C57BL/6 (Th1-prone) and BALB/c (Th2-prone) mouse recipients in an in vivo sensitization model. Two strains of mice were presensitized with Lewis rat splenocytes as xenogeneic antigens. We found that BALB/c recipients mounted a significantly higher total IgG response to the xeno-antigens when compared with C57BL/6 recipients, 10 days after rat splenocyte infusion. A Th2-mediated antibody response with high ratio of IgG1/IgG2a was seen in the BALB/c recipients, while a Th1 antibody response with low ratio of IgG1/IgG2a was detected in C57BL/6 recipients. CD11c(+)DC isolated from C57BL/6 recipients possessed increased expression of CD8alpha(+) (DC-1 type). The administration of bone marrow derived-DC from IL-12 knockout mice into C57BL/6 recipients induced a shift of Th-mediated anti-xenogeneic antibody responses from Th1 to Th2 domain. Our findings suggest that DC could play an important role to regulate the balance of Th1/Th2 cytokine profiles and rejection patterns in xenotransplantation.

Phenotypic and cytolytic activity ofMacaca nemestrina natural killer cells isolated from blood and expanded in vitro

Natural killer (NK) cells from nonhuman primates have not been completely characterized, and methods for expanding nonhuman primates NK cells in vitro have been described only in rhesus species. The purpose of this report was to characterize NK cells in pigtail macaques (Macaca nemestrina), a species that is frequently used in studies of transplantation biology/immunology, virology, vaccine development, and reproductive biology. NK cells from Macaca nemestrina peripheral blood were best defined by the expression of CD16 and CD8alpha, and the absence of CD3. Subsets of these cells express CD56, NKp30, and NKp46. An enhanced ability to kill K562 cells was not present in fluorescence activated cell sorted (FACS)-purified CD16-/CD3+ and CD16-/CD56+ cells isolated from fresh peripheral blood. However, FACS-purified CD16+/CD3- and CD16+/CD56- cells were highly efficient killers of K562 cells. Macaca nemestrina NK cells can be expanded by in vitro culturing of FACS-purified CD16+/CD2-/CD3-/CD56- cells, or from peripheral blood cells depleted of cells expressing CD3, CD4, and HLA-DR. Cells in these cultures expand 70-fold after 21 days of culturing. After culturing, these cells express high levels of natural cytotoxicity receptors (NCRs) NKp30 and NKp46. NK cell populations obtained from FACS-purified CD16+/CD3-, CD16+/CD56- cells and CD3/CD4/HLA-DR-depleted cells were highly efficient killers of K562 cells. These data suggest that a population of highly enriched cytolytic NK cells can be obtained from purified CD16+/CD3- and CD16+/CD56- cells obtained from peripheral blood, as well as from cells that have been cultured and expanded from peripheral blood that is depleted of CD3/CD4/HLA-DR-expressing cells.

Differential capacity of CD8α+ or CD8α− dendritic cell subsets to prime for eosinophilic airway inflammation in the T‐helper type 2‐prone milieu of the lung

Different subsets of dendritic cells (DCs), identified in mouse spleen by their differential expression of CD8 alpha, can induce different T-helper (Th) responses after systemic administration. CD8 alpha(-) DCs have been shown to preferentially induce Th type 2 (Th2) responses whereas CD8 alpha(+) DCs induce Th1 responses. To study if these DC subsets can still induce different Th responses in the Th2-prone milieu of the lung and differentially prime for eosinophilic airway inflammation, typical of asthma. Donor mice first received daily Flt3L injections to expand DC numbers. Purified CD8 alpha(+) or CD8 alpha(-) splenic DCs were pulsed with ovalbumin (OVA) or phosphate-buffered saline and injected intratracheally into recipient mice in which carboxyfluorescein diacetate succinimidyl ester-labelled OVA-specific T cell receptor transgenic T cells had been injected intravenously 2 days earlier. T cell proliferation and cytokine production of Ag-specific T cells were evaluated in the mediastinal lymph nodes (MLNs) 4 days later. The capacity of both subsets of DCs, to prime for eosinophilic airway inflammation was determined by challenging the mice with OVA aerosol 10 days later. CD8 alpha(-) DCs migrated to the MLN and induced a vigorous proliferative T cell response accompanied by high-level production of IL-4, IL-5, IL-10 and also IFN-gamma during the primary response and during challenge with aerosol, leading to eosinophilic airway inflammation. In the absence of migration to the MLN, CD8 alpha(+) DCs still induced a proliferative response with identical levels of IFN-gamma but reduced Th2 cytokines compared with CD8 alpha(-) DCs, which led to weak eosinophilic airway inflammation upon OVA aerosol challenge. Unpulsed DCs did not induce proliferation or cytokine production in Ag-specific T cells. CD8 alpha(-) DCs are superior compared with CD8 alpha(+) DCs in inducing Th2 responses and eosinophilic airway inflammation in the Th2-prone environment of the lung.

Flt3-ligand, IL-4, GM-CSF, and adherence-mediated isolation of murine lung dendritic cells: assessment of isolation technique on phenotype and function.

Lung dendritic cells (DCs) are difficult to study due to their limited quantities and the complexities required for isolation. Although many procedures have been used to overcome this challenge, the effects of isolation techniques on lung DCs have not been reported. The current study shows that freshly isolated DCs (CD11c+) have limited ability to induce proliferation in allogeneic T cells, and are immature as indicated by low cell surface expression of costimulatory molecules compared with liver or splenic DCs. DCs isolated after overnight culture or from mice treated with Flt3L are phenotypically mature and potent stimulators of allogeneic T cells. DCs could not be propagated from lung mononuclear cells in response to IL-4 and GM-CSF. Contrary to data reported for nonpulmonary DCs, expression of CCR6 was decreased on mature lung DCs, and only a subset of mature DCs expressed higher levels of CCR7. Absence of CD8alpha expression indicates that freshly isolated DCs are myeloid-type, whereas mature DCs induced by overnight culture are both "lymphoid" (CD8alpha+) and "myeloid" (CD8alpha-). DCs from mice genetically deficient in CD8alpha expression were strong simulators of allogeneic T cells which was consistent with data showing that CD8alpha- DCs from CD8alpha-sufficient mice are better APCs compared with CD8alpha+ DCs from the same mice. These data show that freshly isolated lung DCs are phenotypically and functionally distinct, and that the isolation technique alters the biology of these cells. Therefore, lung DC phenotype and function must be interpreted relative to the technique used for isolation.

CD8 alpha is an activation marker for a subset of peripheral CD4 T cells.

Rat CD4 T lymphocytes express CD8 alpha upon activation. Here, we show that double-positive cells express CD8 alpha alpha homodimers, and we study their phenotype and function. Most activated CD4(+) lymphocytes expressing CD8 alpha are recent thymic emigrants. Accordingly, most activated CD4 single-positive thymocytes express CD8 alpha, and thymectomy and aging decrease the frequency of CD4(+)CD8 alpha(+) lymphocytes. However, CD8 induction is not restricted to CD4(+) recent thymic emigrants. CD4(+)CD8 alpha(+) and CD4(+)CD8 alpha(-)cells were generated in vitro from naive or from primed donors and, to study their function, were transferred to normal rats. Both cell types helped primary humoral responses, but only CD4(+)CD8 alpha(-) cells promoted secondary responses. Thus, memory CD4 T cells mediating antibody responses and some naive CD4(+) lymphocytes do not express CD8 alpha. In addition, CD4(+)CD8 alpha(+) cells produce mainly Th1 cytokines while CD4(+)CD8 alpha(-) cells produce IL-10 and showed a sustained proliferative response. Hence, CD8 alpha expression after activation distinguishes two distinct CD4 T cell subsets.

Expression of the Mig (CXCL9) gene in murine lung carcinoma cells generated angiogenesis-independent antitumor effects

We examined whether expression of monokine induced by IFN-gamma (Mig, CXCL9) in tumors could produce antitumor effects. Murine lung carcinoma cells (A11) were retrovirally transduced with the murine Mig gene (A11/Mig) and were inoculated into syngeneic mice. Although proliferation in vitro of A11/Mig cells was not different from that of parent cells, the growth in vivo of A11/Mig tumors was significantly retarded compared with that of parent tumors. The antitumor effect was dependent on the amount of Mig produced. We compared the expression level of marker genes of lymphocytes and endothelial cells between parent and A11/Mig tumor masses with reverse transcription-polymerase chain reaction. Expression of CD4, CD8alpha, CD40, CD86, CD28, CD31 and vascular endothelial growth factor was not different between the two tumor groups but expression of CD40 ligand, CD80, NK1.1 and CXCR3 was relatively lower in A11/Mig tumors. Although Mig is a chemotactic factor for activated T and NK cells and an inhibitor for angiogenesis, the present data suggested that production of Mig in tumors did not recruit activated T and NK cells efficiently or suppress angiogenesis. The antitumor effects by Mig could be independent of anti-angiogenesis and recruitment of T and NK cells.

Marked increase in number of dendritic cells in autoimmune-prone (NZW x BXSB)F1 mice with age.

Here, we report that the number of CD11c(+)CD3(-) B220(-) cells increases in autoimmune-prone male (NZW x BXSB)F1 (W/BF1) mice with age. The CD11c(+)CD3(-)B220(-) cells from W/BF1 mice show a typical stellate shape and induce the proliferation of T cells. In the CD11c(+)CD3(-)B220(-) cells from W/BF1 mice, CD11b (Mac-1alpha), NK 1.1, and CD95 (Fas) are upregulated in comparison with normal mice, while the expression of CD8alpha, CD117 (c-kit), CD135 (Flk-2/Flt-3), and Sca-1 decreases. There is a significant increase in Flt-3L (FL) mRNA in the bone marrow of W/BF1 mice with age. Moreover, activated hemopoietic cells express high levels of FL. The injection of CD11c(+)CD3(-)B220(-) cells from old W/BF1 mice to young W/BF1 mice transiently induces autoimmune disease (thrombocytopenia). These results suggest that hyperproduction of FL from activated hemopoietic cells induces a dramatic increase in the number of dendritic cells in aged W/BF1 mice, followed by the acceleration of autoimmunity.

IL-2 down-regulates the expression of TCR and TCR-associated surface molecules on CD8(+) T cells.

CD8(+) T cells are known to down-regulate the TCR complex upon ligation with its cognate MHC class I-peptide complex. In the present report, we demonstrate that stimulation of CD8(+) T cells with cytokines also leads to down-regulation of the TCR complex and TCR-associated surface molecules. A significant reduction of TCRalpha beta, CD3, CD8alpha and CD8beta surface expression was observed when CD8(+) T cells were cultured in IL-2 and to a lesser extent in IL-4 or IL-15. The down-regulation was apparent after 2 days of culture and was observed at IL-2 concentrations as low as 10 U/ml. Using TCR transgenic mice, we found that the down-regulation was associated with a decreased affinity of CD8(+) T cells to MHC class I-peptide complexes, as determined by MHC class I tetramer staining. Furthermore, the antigen-specific proliferation of IL-2-pre-activated CD8(+) T cells was significantly reduced compared to naive CD8(+) T cells or to CD8(+) T cells previously stimulated with peptide-pulsed dendritic cells. Moreover, only CD8alpha(high) but not CD8alpha(low) cells sorted from IL-2-activated CD8(+) T cells proliferated in response to specific antigen, although both subsets proliferated equally well to IL-2. Taken together, these data suggest that the down-regulation of TCR components and a subsequent decrease in affinity towards MHC class I-peptide complexes may be a mechanism by which TCR-dependent proliferation of non-specifically activated CD8(+) T cells is avoided.

Dendritic cell development from common myeloid progenitors.

Dendritic cells (DCs) are professional antigen-presenting cells which both initiate adaptive immune responses and control tolerance to self-antigens. It has been suggested that these different effects on responder cells depend on subsets of DCs arising from either myeloid or lymphoid hematopoietic origins. In this model, CD8 alpha+ Mac-1- DCs are supposed to be of lymphoid while CD8 alpha- Mac-1+ DCs are supposed to be of myeloid origin. Here we summarize our findings that both CD8 alpha+ and CD8 alpha- DCs can arise from clonogenic common myeloid progenitors (CMPs) in both thymus and spleen. Therefore CD8 alpha expression DCs does not indicate a lymphoid origin and differences among CD8 alpha+ and CD8 alpha- DCs might rather reflect maturation status than ontogeny. On the basis of transplantation studies, it seems likely that most of the DCs in secondary lymphoid organs and a substantial fraction of thymic DCs are myeloid-derived.