CD80 and CD86 costimulatory molecules on circulating T cells of HIV infected individuals

The expression of CD80 and CD86 costimulatory molecules, typical for antigen presenting cells (APC), was measured on circulating T cells of 20 HIV-infected individuals and of 11 HIV-negative healthy controls. The CD80 and CD86 molecules were present on both circulating T subsets of HIV-infected individuals (mean of CD80 expression within CD4+ T cells [CD80/CD4]: 5.0%; and CD86/CD4: 2.6%; CD80/CD8 4.1% and CD86/CD8: 2.7%) and were associated with HLA-DR expression. Some CD80 and CD86 expression was also found in normal controls, and only the expression of CD86 was significantly (P < 0.05) increased on CD4 + and CD8 + T cells of HIV-infected individuals. The expression of CD28 was decreased on T cells of HIV-infected individuals and was negatively correlated to the expression of HLA-DR and CD86 (mean CD28 within CD3+T cells: HIV+ 29.5%, HIV - 67.6%; correlation coefficient, - 0.75 and - 0.71, respectively). The more the disease proceeds, the less CD28 and the more DR and CD86 are found on circulating T cells. This suggests that during HIV infection T cells themselves develop an antigen presenting phenotype by upregulating expression of HLA-DR, CD86 and CD80 molecules.     

Active Crohn's Disease Patients Show a Distinctive Expansion of Circulating Memory CD4+CD45RO+CD28null T Cells

In a previous study we found an expansion of circulating memory (CD45RO(+)) CD4(+) T cells in patients with Crohn's disease (CD). The aim of this work was to investigate the phenotypic and functional characteristics of this T-cell subset in CD. We analyzed in peripheral blood CD4(+)CD45RO(+) T cells from CD patients the expression of surface markers associated to immune activation, costimulation, and apoptosis. In sorted CD4(+)CD45RO(+) T cells apoptosis was quantified by fluorescent annexin V binding. Healthy subjects and patients with ulcerative colitis and acute bacterial enterocolitis served as control groups. An increased percentage of memory CD4(+)CD45RO(+) T cells lacking the expression of costimulatory receptor CD28 was detected in patients with active CD when compared to the other groups evaluated. This expanded CD4(+)CD45RO(+)CD28(null) T-cell subset expressed mostly the effector-cell marker CD57(+). Both CD28 downregulation and CD57 expression correlated to CDAI and surrogate markers of disease activity. These phenotypic changes observed on CD4(+)CD45RO(+) T cells from active CD returned to values similar to healthy controls after clinical remission. Moreover, this memory CD28(null) T-cell subset might express more intracytoplasmic TNF and IFN-gamma than their CD28(+) counterpart. Significantly lower frequencies of memory CD4(+)CD45RO(+) T cells expressing CD95 apoptosis receptor were found in patients with active CD. Moreover, sorted CD4(+)CD45RO(+)and CD4(+)CD45RO(+) CD28(null) T cells from patients with active CD exhibited a lower apoptotic rate than that found in healthy controls and inactive CD patients. According to our data, circulating T lymphocytes from active CD patients show distinctive phenotypic and functional changes, characterized by an expansion of memory CD4(+)CD45RO(+)CD28(null) T cells expressing effector-associated cell surface molecules and displaying enhanced resistance to apoptosis.     

Enhanced Expression of CD80 (B7-1), CD86 (B7-2), and CD40 and Their Ligands CD28 and CD154 in Fulminant Hepatic Failure

To define a possible role for changes in the regulation of antigen presentation in fulminant hepatic failure (FHF), we studied the expression of co-stimulatory molecules CD80 (B7-1), CD86 (B7-2), and CD40 along with their ligands CD28 and CD154. We analyzed the liver tissue from patients with FHF (n = 18), chronic liver disease (n = 30), and acute hepatitis (n = 3) and from normal controls (n = 9) by immunohistochemistry and examined the temporal relationship between CD80/CD86 and CD40 expression and disease in the mouse models of galactosamine-lipopolysaccharide and galactosamine-tumor-necrosis-factor-induced FHF. In human controls, faint CD80/CD86 immunoreactivity was restricted to Kupffer cells, and CD40 expression was expressed on bile ducts, macrophages, and sinusoidal endothelial cells (SECs). In FHF, immunoreactivity for CD80 and CD86 was observed on significantly higher numbers of cells, including SECs. Increased CD80/CD86 expression corresponded to increased numbers of CD28-positive lymphocytes. The expression of CD40 was also clearly elevated on virtually all cell types in FHF. In both murine models, CD40 and CD80/CD86 expression was up-regulated before tissue damage could be detected. Our data suggest that up-regulated expression of co-stimulatory molecules might lead to an excessive antigen presentation in FHF as an early step in the pathogenesis before the onset of tissue damage.     

Apoptotic cell death in conjunction with CD80 costimulation confers uveal melanoma cells with the ability to induce immune responses

Uveal melanoma is a rare malignancy with a poor prognosis despite current therapeutic intervention. The current investigation focuses on the immunogenicity of uveal melanoma cells genetically modified with recombinant adenovirus encoding CD80 (AdCD80) in contrast to their parental counterpart. We demonstrate that costimulation provided by uveal melanoma cells improved immune responses in vitro as determined by mixed lymphocyte tumour cell cultures and cytotoxic T-cell assays using lymphocytes from healthy donors and uveal melanoma patients. Flow cytometry revealed T-cell stimulation by activated CD4+ and CD8+ T cells. Additionally, autologous lymphocytes proliferated in response to CD80-expressing primary uveal melanomas, indicating that this patient group is suitable for immunotherapy. Moreover, this study utilized AdCD80 modified and parental apoptotic tumour cells, loaded onto immature dendritic cells, as a source of tumour antigen. The ability of live or apoptotic tumour cells to stimulate lymphocyte proliferation and activation was determined. Apoptotic uveal melanoma cells expressing CD80 were efficient at inducing an immune response and served as a potent immunogen. The use of apoptotic uveal melanoma cells in combination with expression of costimulatory molecules could prove a novel adjuvant therapy for the treatment of this disease.     

Role of CD80, CD86, and CTLA4 on mouse CD4(+) T lymphocytes in enhancing cell-cycle progression and survival after activation with PMA and ionomycin

Cell surface interactions between the T cell costimulatory receptors, CD28 and cytotoxic T-lymphocyte antigen-4 (CTLA4), with their cognate ligands, CD80 and CD86, on antigen-presenting cells play an important role in T cell activation. Although CD80 and CD86 are induced on T cells after activation, not much is known about their role in modulating T cell function. We show that CD80, CD86, and CTLA4 are induced on purified CD4(+) T cells after in vitro activation with phorbol 12-myristate 13-acetate (PMA) and ionomycin, and they play an essential role for proliferation and survival. Blockade of CTLA4-CD80/CD86 interactions greatly reduces PMA and ionomycin-mediated mouse CD4(+) T cell activation. The three key features of this inhibition of activation are: First, late events in T cell activation (after 18 h) are affected; second, these cells do not undergo anergy; and third, CD4(+)CD25(+) regulatory T cells are not responsible. Activation of T cells with PMA and ionomycin together with CTLA4-CD80/CD86 blockade results in decreased induction of CD25 and Bcl-X(L), reduced interleukin (IL)-2, and enhanced transforming growth factor-beta (TGF-beta) production. Furthermore, extended CTLA4-CD80/CD86 blockade results in decreased cell-cycle progression and enhanced apoptosis in a large proportion of cells. This inhibition of T cell proliferation can be rescued completely with anti-CD28 or IL-2 and partially with TGF-beta antagonists. This study reveals a functional role for CD80, CD86, and CTLA4 on CD4(+) T lymphocytes and sheds light on the mechanisms by which these molecules enhance activation and survival with PMA and ionomycin.     

Importance of CD80/CD86-CD28 interactions in the recognition of target cells by CD8+CD122+ regulatory T cells

CD8+CD122+ regulatory T cells are a newly identified, naturally occurring type of regulatory T cell that produce interleukin-10 (IL-10) and effectively suppress interferon-gamma (IFN-gamma) production from both CD8+ and CD4+ target cells. Molecular mechanisms responsible for the recognition of target cells by CD8+CD122+ regulatory T cells were investigated in this study by using an in vitro culture system that reconstitutes the regulatory action of these cells. CD8+CD122( regulatory T cells did not produce IL-10 and did not suppress the IFN-gamma production of allogeneic target T cells when they were stimulated by immobilized anti-CD3 antibody alone, but they clearly produced IL-10 and suppressed the IFN-gamma production of target cells when stimulated by anti-CD3 plus anti-CD28-coated beads. IFN-gamma production by major histocompatibility complex-class I-deficient T cells was also suppressed by CD8+CD122+ regulatory T cells stimulated with anti-CD3 plus anti-CD28 antibody but was not suppressed by cells stimulated by anti-CD3 alone. Experiments examining the blockade of cell surface molecules expressed on either the regulatory cells or the target cells by adding specific neutralizing antibodies in the culture indicated that CD80, CD86, and CD28 molecules were involved in the regulatory action, but cytotoxic T lymphocyte antigen-4, inducible costimulatory molecule (ICOS) and programmed death-1 (PD-1) molecules were not. Finally, CD8+CD122+ cells isolated from CD28-knockout (CD28-/-) mice showed no regulatory activity. These results indicate that CD8+CD122(+) regulatory T cells recognize target T cells via the interaction of CD80/CD86-CD28 molecules to become active regulatory cells that produce suppressive factors such as IL-10.     

Differential function of CD80- and CD86-transfected human melanoma cells in the presence of IL-12 and IFN-gamma

Introduction of co-stimulatory molecules like CD80 and CD86 represents a means to augment the immunogenicity of tumor cells and to induce immune responses directed at tumor antigens. Here we compared CD80- and CD86-transfected human melanoma cells to induce primary immune responses by their capacity to promote proliferation of human allogeneic resting T lymphocytes. CD80- and CD86-transfected SkMel63 melanoma cells induced T cell activation to a comparable degree, which was found to be independent of the cell surface density of these co- stimulatory molecules. Co-expression of CD80 and CD86 did not result in a synergistic increase in T cell proliferation. Both CD80 and CD86 transfectants induced the proliferation of isolated CD4+ or CD8+ T cells. Exogenous IL-2, IL-4 and tumor necrosis factor-alpha respectively enhanced primary T cell proliferation independent of CD80 or CD86 expression. Interestingly, differential activities of CD80 and CD86 were observed following stimulation of resting T cells in the presence of IL-12. Whereas IL-12 increased T cell proliferation in the presence of CD86-transfected melanoma cells, it exhibited an inhibitory function in the presence of CD80-expressing SkMel63 cells. Experimental evidence indicates that this inhibitory effect was mediated by IFN- gamma since (I) IFN-gamma secretion of stimulated T cells was augmented by IL-12, (II) exogenous IFN-gamma also inhibited T cell proliferation induced by CD80- but not CD86-transfected SkMel63 cells and (III) the inhibitory effect of IL-12 was blocked by an anti-IFN-gamma mAb.      

Activation-induced expression of MICA on T lymphocytes involves engagement of CD3 and CD28

MICA is an HLA-related cell stress-regulated antigen recognized by cytotoxic cells expressing the NKG2D molecule. Although resting lymphocytes do not express MICA, it can be induced on PHA-activated T cells. Here, we demonstrate by Western blot that MICA is induced on allogeneic-activated CD4(+) and CD8(+) T lymphocytes. Blocking activation with anti-HLA class I, anti-HLA-DR, or anti-CD86 mAb affected the expression of MICA slightly. When T cells were stimulated with anti-CD3 or anti-CD28 mAb plus PMA, a sustained up-regulation of MICA was observed by Western blot, RT-PCR, and flow cytometry. The expression of MICA reached a plateau at day 4 after CD3 engagement and at day 3 after anti-CD28/PMA stimulation. Conversely, the proliferative response reached a peak at day 4. Hence, CD3 or CD28 engagement induces MICA expression on T lymphocytes. This activation-induced expression might participate in NKG2D-mediated cytotoxicity toward activated T cells to maintain homeostasis during an ongoing immune response.     

Impaired CD4 and CD8 T cell phenotype and reduced chemokine secretion in recent-onset type 1 diabetic children

Although the role of the T cell-mediated autoimmune reaction in type 1 diabetes (T1D) is conclusive, studies including data from human circulating CD4(+) and CD8(+) lymphocytes subsets during the disease onset and posterior development are scarce. Further, chemokines and chemokine receptors are key players in the migration of pathogenic T cells into the islets of non-obese diabetic mice developing T1D, but few studies have investigated these markers in human T1D patients. We studied the expression of T helper 1 (Th1)- and Th2-associated chemokine receptors, and the two isoforms of CD45 leucocyte antigen on CD4(+) and CD8(+) lymphocytes from T1D and healthy children, as well as the secretion of chemokines in cell supernatants in peripheral blood mononuclear cells. Our results showed increased expression of CCR7 and CD45RA and reduced CD45RO on CD8(+) cells among recent-onset T1D patients. The percentages of CD4(+) cells expressing CXC chemokine receptor 3 (CXCR3), CXCR6 and CCR5, and the secretion of interferon-gamma-induced protein-10, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha and MIP-1beta was lower among diabetics. Low expression of Th1-associated receptors and secretion of chemokines, together with an increased amount of CD8(+) cells expressing CD45RA and CCR7 in T1D patients therefore might represent suboptimal Th function in T1D, leading to impaired T cytotoxic responses or alternatively reflect a selective recruitment of Th1 cells into the pancreas.     

Analysis of the CD8-positive T cell response in Japanese patients with chronic hepatitis C using HLA-A*2402 peptide tetramers

Hepatitis C virus (HCV)-specific CD8+ cytotoxic T lymphocytes (CTL) contribute to viral clearance in acute, self-limited hepatitis C as well as to liver cell injury in the more frequent cases with chronic hepatitis C. Although HLA class I-peptide tetramers have been used to detect circulating HCV epitope-specific CTL with a high sensitivity and specificity, this technique has been targeted exclusively to the most frequent HLA haplotypes in the Caucasian population and the large number of HCV-infected Asian patients, most of whom are HLA-A24 positive, have not been studied. The current study determines the frequency, phenotype, and clinical significance of HCV-specific CD8(+) T lymphocytes with five different HLA-A*2402 tetramers in 43 HCV infected Japanese patients and 32 controls. Overall, tetramer(+) cells were detected in the blood of 33 of 43 patients at frequencies of 0.064-0.75% CD8(+)CD4(-)CD14(-)CD19(-) T lymphocytes. Interestingly, although the T cell response was always targeted multispecifically against epitopes in different HCV proteins, the relative frequency of cells stained with individual tetramers differed between patients. Furthermore, tetramer(+)CD8(+) T lymphocytes were highly activated, but the phenotypes of different tetramer(+) cells varied in each patient. In conclusion, HLA-A24 restricted, HCV-specific CD8(+) T lymphocytes are found at similar frequencies in Asian patients as HLA-A2 restricted, HCV-specific CD8(+) T lymphocytes in Caucasian patients. Differences in the frequency and activation status of individual tetramer(+) cell populations suggest that CD8(+) T lymphocytes with different HCV epitope specificity may mediate differential pathogenetic effects in chronic hepatitis C.     

Nonspecific CD4(+) T cells with uptake of antigen-specific dendritic cell-released exosomes stimulate antigen-specific CD8(+) CTL responses and long-term T cell memory

Dendritic cell (DC) and DC-derived exosomes (EXO) have been used extensively for tumor vaccination. However, its therapeutic efficiency is limited to only production of prophylactic immunity against tumors. T cells can uptake DC-released EXO. However, the functional effect of transferred exosomal molecules on T cells is unclear. In this study, we demonstrated that OVA protein-pulsed DC-derived EXO (EXO(OVA)) can be taken up by Con A-stimulated, nonspecific CD4(+) T cells derived from wild-type C57BL/6 mice. The active EXO-uptaken CD4(+) T cells (aT(EXO)), expressing acquired exosomal MHC I/OVA I peptide (pMHC I) complexes and costimulatory CD40 and CD80 molecules, can act as APCs capable of stimulating OVA-specific CD8(+) T cell proliferation in vitro and in vivo and inducing efficient CD4(+) Th cell-independent CD8(+) CTL responses in vivo. The EXO(OVA)-uptaken CD4(+) aT(EXO) cell vaccine induces much more efficient CD8(+) T cell responses and immunity against challenge of OVA-transfected BL6-10 melanoma cells expressing OVA in wild-type C57BL/6 mice than EXO(OVA). The in vivo stimulatory effect of the CD4(+) aT(EXO) cell to CD8(+) T cell responses is mediated and targeted by its CD40 ligand signaling/acquired exosomal CD80 and pMHC I complexes, respectively. In addition, CD4(+) aT(EXO) vaccine stimulates a long-term, OVA-specific CD8(+) T cell memory. Therefore, the EXO(OVA)-uptaken CD4(+) T cells may represent a new, effective, EXO-based vaccine strategy in induction of immune responses against tumors and other infectious diseases.     

CD69, HLA-DR and the IL-2R identify persistently activated T cells in psoriasis vulgaris lesional skin: blood and skin comparisons by flow cytometry

Many lymphocyte-activation-associated molecules are observed by immunohistochemistry in psoriasis vulgaris lesional skin. Non-T cells in lesional skin also express these molecules. We quantitatively measured the number of T cells expressing cell surface activation-associated molecules (CD69, CD25, CD122, HLA-DR) and co-stimulatory molecules (CD28, CTLA-4, CD80, CD86), including a Type 2 T cell marker (CD30) and CD11b, by flow cytometry of skin and peripheral blood. T cells in single cell suspensions of psoriatic lesional-epidermis-expressed HLA-DR (86%), CD69 (59%), CD25 (55%), CD122 (44%), and CD28 (91%). Dermal T cells showed similar percentages except for CD69 (17%). CD69 was found directly in lesional skin biopsies by immunohistochemistry. Both CD4 and CD8 subsets from lesional skin contained large populations of CD25+ cells with a bias towards CD8 activation in the epidermis and towards CD4 activation in the dermis. CD86, CD80, CTLA-4, CD30 and CD11b were expressed by less than 23% of the T cell populations from both the epidermis and dermis. CD30+CD4+ cells were found two-fold over CD8+ T cells. These results show that the majority of lesional lymphocytes are persistently activated. We also found the majority of Type 2 associated markers primarily on the CD4+ epidermal T cell population. Psoriatic blood contained elevated levels of T cells expressing CD25, primarily within the CD8+ subset. Thus the majority of lesional T cells expressed the three primary activation markers, while psoriatic blood T cells were distinguished by an increase in CD25, specifically within the CTL population.     

Lower percentage of CD8(high+)CD152(+) but not CD8(high+)CD28(+) T lymphocytes in the elderly may be reverted by interleukin 2 in vitro

An expression of the surface co-stimulatory molecules-the CD152 and the CD28 has been compared between young and old individuals on the CD8(high+) lymphocytes. Sixty five elderly healthy (65-96 years old) and 31 young (19-40 years old) volunteers were examined. An expression of CD152 and CD28 surface antigens was analyzed by flow cytometry ex vivo and on whole blood cell cultures lymphocytes stimulated with interleukin 2 (IL2). The elderly population was characterized by a lower percentage of the CD8(high+) lymphocytes than the young population. The percentages of CD28(+) lymphocytes as well as those of CD8(high+)CD28(+) subpopulation were lower in the old group compared to the young group. The surface expression of CD152 antigen was similar to that of CD28 with a lower percentage of the CD152(+) lymphocytes and CD8(high+)CD152(+) cells in the old group. Stimulation of lymphocytes in vitro with IL2 resulted in an increase of the CD8(high+)CD152(+) cells in the elderly, while it had no effect on lymphocytes of the young group. Our results indicate that lymphocytes of the elderly population are characterized by a lower expression of the surface CD28 and CD152 molecules. An age-related decrease of an expression of the co-stimulatory molecules CD28 and CD152 on the surface of lymphocytes, found in our study, may be compatible with a hypothesis of a 'remodelling' of immune response in the healthy elderly.     

Interleukin-12 neutralization alters lung inflammation and leukocyte expression of CD80, CD86, and major histocompatibility complex class II in mice infected with Histoplasma capsulatum

Histoplasma capsulatum induces a cell-mediated immune response in lungs and lymphoid organs of mammals. Resolution of primary infection in mice depends on interleukin-12 (IL-12), since neutralization of this monokine increases susceptibility to infection. The present study was designed to determine if blockade of IL-12 disrupts the protective immune response by altering the influx of lineage-specific cells into infected lungs and the numbers of cells expressing CD80, CD86, CD119, and major histocompatibility complex class II (MHC II) molecules. In mice given anti-IL-12, there was a 2.5-fold decrease in total numbers of T cells on days 3 to 10 of infection and a 4-fold increase in Mac-1/Gr-1(+) cells on days 7 and 10 compared to infected controls. CD80(+) lung cells from anti-IL-12-treated mice were 2- to 3-fold greater than those from controls on days 7 and 10, whereas the total numbers of CD86(+) cells were 2- to 3-fold less and MHC II(+) cells were 1.5- to 2-fold less on days 3 and 5. Cells expressing CD119 were reduced 1.5-fold on day 5. Treatment with monoclonal antibodies (MAb) to CD80, CD86, or both reduced the fungal burden slightly compared to that in rat immunoglobulin G-treated controls, whereas after IL-12 neutralization, blocking of CD80 reduced the tissue burden by 2. 5-fold and this correlated with a decrease in IL-4. Regardless, mortality was not altered by treatment with MAb to CD80 or CD86. We conclude that (i) IL-12 neutralization alters the nature of the inflammatory response in lungs and the expression of CD80 and CD86 on lineage-specific cells, (ii) the immune response during infection with H. capsulatum is controlled via mechanisms independent of the CD80 and CD86 costimulatory pathways, and (iii) decreased expression of CD86 and MHC II may modulate generation of optimal protective immunity.     

Experimental infection with Trypanosoma cruzi increases the population of CD8(+), but not CD4(+), immunoglobulin G Fc receptor-positive T lymphocytes

It is well established that activating-type Fc receptors for immunoglobulin G (FcgammaR), such as FcgammaRI and FcgammaRIII, are essential for inducing inflammatory responses. On the other hand, a unique inhibitory FcgammaR, FcgammaRIIB, inhibits intracellular signaling upon engagement of immunoglobulin G-immune complexes, suppressing inflammation and autoimmunity. The expression of FcgammaRIIB on B lymphocytes, natural killer cells, macrophages, mast cells, and a number of other cell types has been demonstrated for many years. However, the expression on T lymphocytes is probably restricted to activated cells in a narrow window of time. The controversy regarding the FcgammaR expression on T lymphocytes is attributable to considerable heterogeneity of cellular subpopulations and activation stages during immune responses in vivo. We addressed here this question by using mice experimentally infected with Trypanosoma cruzi, and we found an increase in the CD8(+) FcgammaR(+) population but not in the CD4(+) FcgammaR(+) population. Moreover, CD8(+) FcgammaR(+) T cells predominantly composed the cardiac inflammatory infiltration induced by the infection. These results indicate a novel pattern of FcgammaR expression on T cells in a pathological situation, and possible functional roles of this phenomenon are discussed.     

Role of new population of peripheral CD11c(+)CD8(+) T cells and CD4(+)CD25(+) regulatory T cells during acute and remission stages in rheumatoid arthritis patients.

BACKGROUND AND PURPOSE: Rheumatoid arthritis (RA) is a CD4(+)-dependent chronic systemic inflammatory disease with autoimmune features. Autoreactive CD4(+) T-cell activation can result in autoimmune diseases. One of the key regulators is the CD4(+)CD25(high) regulatory T (Treg) cell. In an animal arthritis model, CD11c(+)CD8(+) T cells were found to be elevated, and could suppress pathogenic CD4(+) T cells after cross-linking with CD137. The purpose of this study was to compare the expression of CD137, CD4(+)CD25(high) Treg cells, and CD11c(+)CD8(+) in the peripheral blood T lymphocytes of RA patients during active and remissive states, and evaluate the correlation with disease activity. METHODS: Thirty nine RA patients treated at the rheumatology outpatient clinic at the Changhua Christian Hospital were assessed clinically for disease activity and classified as either highly active or remissive by the Disease Activity Score 28. Peripheral blood mononuclear cells were isolated from these patients and compared against normal controls. RESULTS: The presence of CD11c(+)CD8(+) T cells or the expression of CD137 molecules in peripheral blood cells was not related to disease activity. In contrast, CD4(+)CD25(high) Treg cell levels were increased significantly in patients with active RA compared with patients with remissive RA or controls (p<0.05). These lymphocytes were intact, without evidence of apoptosis. CONCLUSIONS: Our results indicate that CD4(+)CD25(high) Treg cells play an important role in modulating RA disease activity and can serve as a parameter of disease activity.     

CD80/CD28 co-stimulation in human brucellosis

Despite treatment, 10-30% of brucellosis patients develop chronic disease, characterized by atypical clinical picture and/or relapses. A defective T helper 1 (Th1) response and a low [corrected] percentage of CD4(+)/CD25(+) cells have been described in chronic brucellosis patients. CD80/CD28 co-stimulation is critical for an efficient Th1 response and has not been studied previously in human brucellosis. In order to investigate the role of CD80/CD28 co-stimulation, 13 acute brucellosis patients (AB), 22 chronic brucellosis patients (CB, 12/22 relapsing type-CB1 and 10/22 atypical type-CB2), 11 'cured' subjects and 15 healthy volunteers (controls) were studied. The percentage of CD4(+)/CD28(+) T lymphocytes and CD14(+)/CD80(+) monocytes were analysed by flow cytometry both ex vivo and after phytohaemagglutinin (PHA)-stimulation with or without heat-killed Brucella abortus (HkBA). Ex vivo analysis showed no differences between all groups studied. PHA stimulation up-regulated the percentage of CD80(+) monocytes in AB compared to 'cured' subjects and controls (P < 0.001), although the proportion of CD4(+)/CD28(+) cells did not alter. A higher percentage of CD80(+) monocytes was observed in the CB1 subgroup, compared to AB, 'cured' subjects and controls (P = 0.042, < 0.001 and < 0.001, respectively). CB2 was characterized by a lower percentage of CD80(+) monocytes in comparison to CB1 (P = 0.020). HkBA in PHA cultures down-regulated the percentage of CD80(+) monocytes compared to PHA alone in all groups, especially in AB and CB patients (P < 0.001 and P = 0.007, respectively). In conclusion, the diminished percentage of CD4(+)/CD25(+) T cells in CB is not associated with inadequate CD80/CD28 co-stimulation. We speculate that differential frequency of CD80(+) monocytes after PHA stimulation could serve as a qualitative parameter of disease status, related to the different clinical forms of chronic brucellosis.     

Cross-regulation of CD86 by CD80 differentially regulates T helper responses from Mycobacterium tuberculosis secretory antigen-activated dendritic cell subsets

We report that stimulation of Mycobacterium tuberculosis secretory antigen- and tumor necrosis factor alpha-matured BALB/c mouse bone marrow dendritic cells (BMDCs) with anti-CD80 monoclonal antibody up-regulated CD86 levels on the cell surface. Coculture of these BMDCs with na?ve, allogeneic T cells now down-regulated T helper cell type 1 (Th1) responses and up-regulated suppressor responses. Similar results were obtained with splenic CD11c(+)/CD8a(-) DCs but not to the same extent with CD11c(+)/CD8a(+) DCs. Following coculture with T cells, only BMDCs and CD11c(+)/CD8a(-) DCs and not CD11c(+)/CD8a(+) DCs displayed increased levels of surface CD86, and further, coculturing these DCs with a fresh set of T cells attenuated Th1 responses and increased suppressor responses. Not only na?ve but even antigen-specific recall responses of the Th1-committed cells were modulated by DCs expressing up-regulated surface CD86. Further analyses showed that stimulation with anti-CD80 increased interleukin (IL)-10 and transforming growth factor-beta-1 levels with a concomitant reduction in IL-12p40 and interferon-gamma levels from BMDCs and CD11c(+)/CD8a(-) DCs and to a lesser extent, from CD11c(+)/CD8a(+) DCs. These results suggest that cross-talk between costimulatory molecules differentially regulates their relative surface densities leading to modulation of Th responses initiated from some DC subsets, and Th1-committed DCs such as CD11c(+)/CD8a(+) DCs may not allow for such modulation. Cognate antigen-presenting cell (APC):T cell interactions then impart a level of polarization on APCs mediated via cross-regulation of costimulatory molecules, which govern the nature of subsequent Th responses.