Genomic organization of the gene coding for the costimulatory human B-lymphocyte antigen B7-2 (CD86)

Impact of Single-Nucleotide Polymorphisms of CTLA-4, CD80 and CD86 on the Effectiveness of Abatacept in Patients with Rheumatoid Arthritis

Abatacept (ABA) is used as a first-line treatment in patients diagnosed with moderate and severe rheumatoid arthritis (RA). The interindividual response to ABA therapy is very variable in these patients. The objective of our study was therefore to investigate the role of polymorphisms of the CTLA-4, CD80 and CD86 genes, as well as that of clinical factors of the disease, in the response to ABA in patients with RA. A retrospective cohort study was carried out in 109 patients receiving treatment with ABA and diagnosed with RA. The genetic variables were analyzed using real-time PCR with TaqMan^® probes. The patients were classified according to the European League Against Rheumatism (EULAR) criteria at 6 and 12 months from start of treatment. The independent variables associated with higher EULAR response were lower duration of previous biologic disease-modifying anti-rheumatic drugs and lower baseline values of the disease activity score 28 after 6 months of ABA treatment; and lower baseline patient’s visual analogue scale (PVAS) after 12 months. In addition, a significant association was found between duration of ABA treatment, non-administration of concomitant glucocorticoids and lower baseline values of the number of inflamed joints and erythrocyte sedimentation rate clinical variables, with remission of the disease after 6 months’ treatment with ABA. Finally, remission of the disease after 12 months’ treatment with ABA was associated with earlier age at start of ABA therapy and lower number of previous biologic therapies (BTs). The CTLA-4rs5742909-T allele and the CTLA-4rs231775-G allele were found to be associated with satisfactory EULAR response and low disease activity (LDA) after 12 months’ treatment with ABA (CTLA-4rs5742909 T vs. CC; OR = 5.88; CI_95% = 1.48–23.29 and OR = 4.75; CI_95% = 1.35–17.94, respectively, and CTLA-4rs231775 G vs. AA, OR = 3.48; CI_95% = 1.20–10.09 and OR = 4.68; CI_95% = 1.49–17.94, respectively). In conclusion, patients with RA treated with ABA showed better EULAR response and LDA rate when they had the CTLA-4 rs5742909-T or CTLA-4 rs231775-G polymorphisms; furthermore, this remission rate increased in patients that began ABA treatment earlier, those with a lower number of previous BTs and those with a lower PVAS value.

Multiple sclerosis risk variants alter expression of co-stimulatory genes in B cells

The increasing evidence supporting a role for B cells in the pathogenesis of multiple sclerosis prompted us to investigate the influence of known susceptibility variants on the surface expression of co-stimulatory molecules in these cells. Using flow cytometry we measured surface expression of CD40 and CD86 in B cells from 68 patients and 162 healthy controls that were genotyped for the multiple sclerosis associated single nucleotide polymorphisms (SNPs) rs4810485, which maps within the CD40 gene, and rs9282641, which maps within the CD86 gene. We found that carrying the risk allele rs4810485*T lowered the cell-surface expression of CD40 in all tested B cell subtypes (in total B cells P ≤ 5.10 × 10⁻⁵ in patients and ≤4.09 × 10⁻⁶ in controls), while carrying the risk allele rs9282641*G increased the expression of CD86, with this effect primarily seen in the naïve B cell subset (P = 0.048 in patients and 5.38 × 10⁻⁵ in controls). In concordance with these results, analysis of RNA expression demonstrated that the risk allele rs4810485*T resulted in lower total CD40 expression (P = 0.057) but with an increased proportion of alternative splice-forms leading to decoy receptors (P = 4.00 × 10⁻⁷). Finally, we also observed that the risk allele rs4810485*T was associated with decreased levels of interleukin-10 (P = 0.020), which is considered to have an immunoregulatory function downstream of CD40. Given the importance of these co-stimulatory molecules in determining the immune reaction that appears in response to antigen our data suggest that B cells might have an important antigen presentation and immunoregulatory role in the pathogenesis of multiple sclerosis.

Genetic association between CD86 polymorphisms and the risk of sepsis in a Chinese Han population

BACKGROUND

Sepsis is a clinical syndrome that is frequently observed after injury or infection, representing a leading cause of mortality worldwide. CD86 (B7-2) is a co-stimulatory molecule on antigen-presenting cells, and plays critical roles in immune responses.

METHODS

A total of 135 sepsis patients and 151 healthy controls were recruited in the current case-control study. Hardy-Weinberg equilibrium (HWE) conformity was examined to assess the representativeness of the study population. CD86 gene polymorphisms were genotyped using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The relative expression of CD86 mRNA was estimated via quantitative real-time PCR (qRT-PCR). Chi-square test was performed to estimate the associations between CD86 gene polymorphisms and sepsis risk, and the results were presented through odds ratio (OR) and 95% confidence intervals (CI).

RESULTS

The genotype distributions of CD86 polymorphisms in the case and control groups conformed to HWE. The GA genotype of the polymorphism rs1129055 was significantly correlated with an increased risk of sepsis (OR = 2.540, 95%CI = 1.288-5.008). The TT genotype of rs1915087 was a risk factor for sepsis (OR = 2.769, 95%CI = 1.292-5.935). High linkage disequilibrium was observed between the two polymorphisms (D' = 1.0, r² = 0.955). However, no significant association was observed between CD86 polymorphisms and its gene expressions (P > 0.05 for all).

CONCLUSION

CD86 gene polymorphisms rs1129055 and rs1915087 may increase the risk of sepsis.

Association between co-stimulatory molecule gene polymorphism and acute rejection of allograft

Co-stimulatory molecules play important roles in T cell-mediated immune response and transplantation. Numerous epidemiological studies have evaluated the association between CD28, CTLA-4 gene variant and allograft rejection. However, the results of these studies on the association remain conflicting. The main purpose of this study was to integrate previous results and explore whether the CD28 IVS3 +17T/C variant, CTLA-4, CD86 and PDCD1 gene polymorphisms were associated with allograft rejection susceptibility. PubMed and Embase (before 2014-3-25), were searched for studies on the relationship of CD28, CTLA-4, CD86 and PDCD1 gene polymorphisms and the incidence of allograft rejection susceptibility. Eligible articles were included for data extraction. The main outcome was the frequency of co-stimulate molecule gene polymorphisms between rejection and non-rejection populations. Comparison of the distribution of SNP was mainly performed using Review Manager 5.0. The odds ratio (OR) and its 95% confidence interval (95% CI) were used to assess the strength of association. Significant associations of the CD28 IVS3 +17T/C variant with acute allograft rejection susceptibility were found (CC +CT/TT OR, 1.45; 95% CI, 1.08-1.94; P=0.01). Also we found an association of the CD28 IVS3 +17T/C variant with kidney allograft rejection cases (CC +CT/TT OR, 1.72; 95% CI, 1.19-2.49; P=0.004) and (C allele OR, 1.74; 95% CI, 1.11-2.75; P=0.02), but not established for liver allograft rejection cases (CC +CT/TT OR, 1.19; 95% CI, 0.47-2.98; P=0.72) and (C allele OR, 0.96; 95% CI, 0.67-1.39; P=0.84). And we found an association of the CD86 +1057G/A variant with non-allograft rejection cases (AA +AG/GG OR, 0.35; 95% CI, 0.14-0.85; P=0.02). This meta-analysis demonstrates that the CD28 IVS3 +17T/C variant might increase acute allograft rejection risk in kidney transplant but not in liver transplant, and there was an association between CD86 +1057G/A variant and reduced acute rejection risk. Further studies will be needed to confirm our findings.

CD86 +1057G/A polymorphism and risk of chronic immune thrombocytopenia

The G to A transition at position +1057 single nucleotide polymorphism site in CD86 gene results in the alanine to threonine substitution, which further affects the antigen-presenting cells' signal transduction. Thus, the purpose of this study was to determine the association between CD86 +1057G/A polymorphism and the risk for chronic immune thrombocytopenia (cITP). The CD86 +1057G/A polymorphism in 158 cITP patients and 150 healthy controls were detected by polymerase chain reaction restriction fragment length polymorphism and then confirmed by DNA sequencing. In the patients with cITP, the frequencies of GG, AG and AA genotypes and G and A alleles were 18.4%, 58.8%, 22.8%, 47.8% and 52.2%, respectively. No difference in genotype and allele frequencies was detected in total cITP patients and normal controls (p = 0.913 and 0.845, respectively). Cases were subsequently classified by age at diagnosis, gender or clinical responses to glucocorticoids, and still no obvious discrepancy of genotype and allele frequencies was found between each of the groups and normal controls. In conclusion, this study suggests that CD86 +1057G/A polymorphism may be not associated with the genetic susceptibility to cITP in a Chinese population.

CD86 + 1057G/A polymorphism and susceptibility to osteosarcoma

CD86 (B7-2), one of the costimulatory molecules on antigen-presenting cells, plays essential roles not only in autoimmunity and transplantation but also in tumor immunity. CD86 + 1057G/A polymorphism (rs1129055) is associated with various diseases. The objective of this study was to investigate the association between CD86  + 1057G/A polymorphism and susceptibility to osteosarcoma in a Chinese population. The CD86 + 1057G/A mutation was detected by polymerase chain reaction-restriction fragment length polymorphism in 205 osteosarcoma cases and 216 age-matched healthy controls. Frequencies of CD86 + 1057 AA genotype and +1057 A allele were significantly increased in osteosarcoma patients than in healthy controls (odds ratio = 2.18, 95% confidence interval, 1.21-3.93, p = 0.008; and odds ratio = 1.43, 95% confidence interval, 1.08-1.88, p = 0.011). Our data suggest that the +1057G/A polymorphism of the CD86 gene is associated with increased susceptibility to osteosarcoma.

CD86 +1057 G/A polymorphism and the risk of colorectal cancer

CD86 (B7-2), one of the costimulatory molecules on antigen-presenting cells, plays essential roles not only in autoimmunity and transplantation but also in tumor immunity. The purpose of this study was to investigate whether CD86 gene polymorphism was involved in predisposing an individual to colorectal cancer (CRC). The CD86 +1057 G/A polymorphism was genotyped by performing polymerase chain reaction-restriction fragment length polymorphism in 273 patients with CRC and 292 healthy controls. There were significant differences in the genotype and allele distribution of +1057 G/A polymorphism of the CD86 gene between cases and controls. The +1057 AA genotype was associated with a significantly increased risk of CRC when compared with the GG genotype (odds ratio [OR] = 2.16; 95% confidence interval [CI], 1.31-3.58). Using the G allele as a reference, a significant correlation was detected between the presence of the A allele and a risk of developing CRC (OR = 1.42; 95% CI, 1.12-1.80). Interestingly, the A allele in female patients with CRC was significantly higher than that in male patients after stratified analysis (OR = 1.49; 95% CI, 1.04-2.14). These data suggest that CD86 +1057G/A polymorphism may contribute to genetic susceptibility to CRC in a Chinese population.

A functional CD86 polymorphism associated with asthma and related allergic disorders

BACKGROUND

Several studies have documented a substantial genetic component in the aetiology of allergic diseases and a number of atopy susceptibility loci have been suggested. One of these loci is 3q21, at which linkage to multiple atopy phenotypes has been reported. This region harbours the CD86 gene encoding the costimulatory B7.2 protein. The costimulatory system, consisting of receptor proteins, cytokines and associated factors, activates T cells and regulates the immune response upon allergen challenge.

METHODS

We sequenced the CD86 gene in patients with atopy from 10 families that showed evidence of linkage to 3q21. Identified polymorphisms were analysed in a subsequent family-based association study of two independent Danish samples, respectively comprising 135 and 100 trios of children with atopy and their parents. Functional analysis of the costimulatory effect on cytokine production was performed in an autologous cell-based system based on cells expressing CD86 variants.

RESULTS

Two polymorphisms were identified, encoding the amino acid changes Ile179Val and Ala304Thr, respectively. Significant associations were observed between the Ile179Val polymorphism and allergy phenotypes in both samples (eg, asthma, p = 4 x 10(-3) in the two samples combined). The undertransmitted (protective) Val179 allele was found to induce higher production of both Th1 and Th2 cytokines than the overtransmitted (risk) Ile179 allele, suggesting a functional impact of the polymorphism.

CONCLUSION

The CD86 gene, and specifically the Ile179Val polymorphism, may be a novel aetiological factor in the development of asthma and related allergic disorders.

Molecular cloning of multiple forms of the ovine B7-2 (CD86) costimulatory molecule

To facilitate analysis of the role of costimulatory molecules in the ovine immune system, we cloned and sequenced eight putative alternatively spliced transcripts of the sheep CD86 (B7-2) costimulatory molecule. Using RT-PCR and rapid amplification of cDNA ends (RACE), we cloned the sheep CD86 (B7-2) molecule that encodes eight forms, which differ in the length of the signal peptide, the presence or absence of a transmembrane region and in their cytoplasmic tails. Comparison of the deduced amino acid sequence of the largest ovine CD86 TM form (CD86-2) with the sequence of cattle, pig, human and mouse CD86 indicated that the deduced protein had a higher degree of similarity to cattle (85% of amino acid identity) than to pig (77%), human (59%), and mouse sequence (45% of identity). Our results indicate that mRNA transcripts encoding different CD86 protein forms are expressed in sheep, like in other mammals, and suggest that the expression of this gene may be regulated at the transcriptional or RNA splicing level, which could give rise to tissue-specific expression of CD86. It is possible that, in the sheep, these CD86 mRNA variants could play different regulatory roles in T cell activation.

Evaluation of CD86 gene polymorphism at +1057 position in liver transplant recipients

BACKGROUND

Efficient T cell-APC interaction requires the participation of primary and co-stimulatory signals. The main co-stimulatory pathway involves the interaction of CD80 and CD86, expressed on the APCs, with their T cell counter-receptor, CD28 and CTLA-4. Recently, a G to A transition has been described at position +1057 of the CD86 gene, located in their cytoplasmic tail.

METHODS

CD86 polymorphism was analyzed by sequence based typing in DNA samples obtained from 205 liver transplant recipients. Acute rejection and chronic rejection were diagnosed based upon conventional clinical, biochemical and histological criteria.

RESULTS

The study of CD86 +1057 (G/A) polymorphism revealed that recipients bearing the A allele or the AA genotype have a reduced risk of acute rejection. In fact, the AA genotype was absent in the group of patients showing acute rejection episodes, whereas its frequency in those patients without acute rejection episodes was 8.8% (P=0.009, OR=0.07). This polymorphism did not reveal any association with the incidence of chronic rejection, but patients bearing the AA genotype showed a higher graft survival rate (83.3%) than those bearing the GA genotype (49.3%) or GG genotype (56.5%).

CONCLUSIONS

The results of the present report suggest that the CD86 AA genotype at +1057 position could be involved in liver transplant acceptance, given that its presence is related to a decrease of acute rejection frequency and to a graft survival increase.

Reactivity of Langerhans cells in human reconstructed epidermis to known allergens and UV radiation

Epidermal Langerhans cells are the outmost guards of our immune defence system. These cells are directly involved in phenomena such as contact hypersensitivity and UV-induced immunosuppression. Some years ago we succeeded in introducing CD34(+)-derived Langerhans cells into a reconstructed human epidermis. Here we describe their reactivity after topical exposure of the reconstructed epidermis to known allergens, allergen-inducible cytokines, irritants and UV irradiation. Exposure to allergens for 24 h resulted in an activated appearance of the Langerhans cells and in some cases a decrease in their number. Concomitantly, IL-1beta and CD86 mRNA over-expressions were detected in the reconstructed epidermis. A topical treatment with TNF-alpha or IL-1beta revealed that both cytokines induced an activated appearance of the Langerhans cells as early as 4 h following application. Irritants had no effect on the integrated Langerhans cells. Exposure of the reconstructed epidermis to Solar Simulated Radiation caused a dramatic decrease in the number of Langerhans cells and a loss of dendricity in the remaining cells 24 h after irradiation. The topical application of a large spectrum UVA/B filter before irradiation prevented these UV-induced alterations. In our hands, this model provides a promising tool to evaluate the sensitization potential of new compounds and to validate the efficacy of sunscreens to prevent UV-induced immunosuppression.

A homogeneous high-throughput genotyping method based on competitive hybridization

OBJECTIVES

A reliable high-throughput assay system is necessary for the analysis of the ever-increasing numbers of single-nucleotide polymorphisms (SNP) relevant to genetic screening studies. We describe an assay suitable also for large-scale screening programs.

DESIGN AND METHODS

The one-step assay is based on asymmetric PCR amplification of the target sequence and subsequent time-resolved fluorescence measurement. Asymmetric amplification results in a single-stranded PCR product that is detected in the amplification vessel with a highly sensitive, homogeneous hybridization method.

RESULTS

A dual label, homogeneous high-throughput platform for nucleic acid sequence analysis was developed and validated using a C/T single-nucleotide polymorphism in the insulin gene as a model analyte and applied also to two other SNP-assays (poliovirus receptor A/G-polymorphism and CD86-gene exon 2 A/G-polymorphism).

CONCLUSIONS

The described high-throughput genotyping technology is very competitive in price, simple in design and easily applied to any analyte sequence.

IL-4-dependent CD86 expression requires JAK/STAT6 activation and is negatively regulated by PKCdelta

CD86 expression is up-regulated in activated monocytes and macrophages by a mechanism that is not clearly defined. Here, we report that IL-4-dependent CD86 expression requires activation of ERK1/2 and JAK/STAT6 but is negatively regulated by PKCdelta. PMA differentiated U937 monocytic cells when stimulated with IL-4 increased CD11b and CD86 expression by 52- and 98-fold, respectively. PMA+IL-4 treatment also induced a synergistic enhancement of ERK1/2 activation when compared to the effects of PMA and IL-4 alone. Use of the mitogen or extracellular kinase (MEK) inhibitor, PD98059, completely blocked up-regulation of CD11b and CD86 demonstrating the importance of MEK-activated ERK1/2. JAK inhibition with WHI-P154-abrogated IL-4-dependent CD11b and CD86 up-regulation and inhibited STAT6 tyrosine phosphorylation. Importantly, CD11b and CD86 expression were not reliant on IL-4-dependent activation of phosphatidylinositol 3'-kinase (PI 3-kinase). Blockade of PKCdelta activation with rottlerin prevented CD11b expression but lead to a 75- and 213-fold increase in PMA and PMA+IL-4-dependent CD86 expression, respectively. As anticipated, increasing PKCdelta activity with anti-sense reduction of CD45 increased CD11b expression and reduced CD86 expression. Likewise, rottlerin prevented nuclear localization of activated PKCdelta. We conclude from these data that IL-4-dependent CD11b expression relies predominantly on enhanced activation of ERK1/2, while IL-4-dependent CD86 expression utilizes the JAK/STAT6 pathway.

Interleukin-1beta converting enzyme subfamily inhibitors prevent induction of CD86 molecules by butyrate through a CREB-dependent mechanism in HL60 cells

To investigate the underlying mechanism for induction of CD86 molecules, we analysed the ability of the histone deacetylase (HDAC) inhibitor, sodium butyrate (NaB), to induce CD86 at the transcriptional level in HL60 cells. Our studies showed that the expression of CD86 on the cell surface was increased by 24 hr of NaB treatment, and the enhancement of CD86 mRNA expression was observed by real-time polymerase chain reaction. When we measured NF-kappaB binding activity, significant activity was induced upon NaB stimulation, which was suppressed by the addition of pyrrolidine dithiocarbamate. Butyrate also induced phosphorylated cAMP response element-binding protein (CREB), which bound to cAMP-responsive elements. Dibutyryl (db) -cAMP induced active CREB and increased the levels of CD86 by 24 hr. These observations indicated that NF-kappaB and/or CREB are crucial for butyrate-dependent activation of CD86 gene expression. We examined the inhibitory effects of various caspase inhibitors on the expression of CD86 in cells treated with NaB, because NaB also induced apoptosis with slow kinetics. Intriguingly, our results demonstrated that inhibitors of the interleukin-1beta converting enzyme subfamily (caspase-1, -4, -5 and -13) blocked the butyrate-induced increase in level of CD86. These inhibitors interfered with CD86 gene transcription in the presence of activated NF-kappaB, whereas phosphorylated CREB was down-regulated in the reactions where these inhibitors were added to inhibit CD86 gene expression. These results suggested that butyrate not only acetylates histones on the CD86 promoter through the suppression of HDAC activity, but that butyrate also regulates CREB-mediated transcription, possibly through the caspase activities triggered by NaB.

Novel transcripts encoding secreted forms of feline CD80 and CD86 costimulatory molecules

Engagement of costimulatory molecules such as CD28 or CD152 (CTLA4) on T cells by CD80 (B7-1) or CD86 (B7-2) dictates the nature of T cell-mediated immune responses. We previously reported the discovery of naturally occurring forms of canine CD80 and CD86 mRNAs which encode secreted CD80 and CD86 molecules. We report here that mRNAs for secreted forms of CD80 and CD86 are also expressed in cats. The mRNA for secreted feline CD86 is generated by deleting a transmembrane domain exon, which is the same mechanism we described for secreted canine CD86. We also identified a feline CD80 transcript that only retains the immunoglobulin variable-like domain. The detection of naturally occurring mRNAs encoding secreted CD80 and CD86 adds further complexity to the regulation of the B7-CD28/CD152 costimulatory pathway.

Identification of an alternatively spliced variant of human CD86 mRNA

CD86 is a costimulatory molecule constitutively expressed by human antigen presenting cells which interacts with CD28 and CTLA-4 expressed by T cells. We have recently reported the identification of an alternatively spliced CD86 mRNA variant (CD86deltaTM) characterized by the deletion of exon 6 which encodes for the transmembrane domain. We report here the identification of an alternatively spliced variant (called CD86deltaEC) expressed by nonstimulated human monocytes and characterized by the deletion of exons 4 and 5 which encode for the extracellular V-like and C-like domains, respectively. The activation of monocytes by IFNgamma (i) induces the preferential expression of the transcript encoding for the membrane form and (ii) increases the expression of CD86 and of the accessory molecules CD40, CD49d and CD54. These results suggest that resting human monocytes may constitutively express different forms of CD86 which can then influence the activation of T cells.

Soluble CD86 is a costimulatory molecule for human T lymphocytes

CD86 is an important costimulatory molecule for the priming and activation of naive and memory T cells, respectively. Here, we show that soluble CD86 is detected in human serum. Soluble CD86 is produced by resting monocytes and results from an alternatively spliced transcript (CD86deltaTM) characterized by deletion of the transmembrane domain. Recombinant CD86deltaTM binds to CD28 and CTLA-4 and induces the activation of T cells after stimulation with anti-CD3 mAb. CD86deltaTM also induces IFNgamma production by virus-specific CD8+ memory human T cells stimulated with the Flu M1 peptide. The concentrations of soluble CD86 found in human serum are sufficient to induce biological activity. Soluble CD86 molecule, therefore, appears to be a functional costimulatory molecule playing a potentially important role in immune surveillance.

Cloning and functional characterization of the 5'-regulatory region of the human CD86 gene

The induction of CD86 expression by IFN-gamma on the surface of various antigen presenting cells has been previously reported. In order to understand the mechanisms by which the expression of the CD86 gene is regulated by IFN-gamma at the transcriptional level, we have cloned and characterized the 5'-flanking region of the human CD86 gene. To functionally analyze the upstream regulatory region of the CD86 gene, a series of luciferase reporter gene constructs were prepared and used for transfection of cells from the monocytic line U937 and Raji B cell line. Under basal conditions, functional activity of these constructs was detected in Raji cells, which show high constitutive expression of the CD86 molecule, but not in U937 cells, which show low expression of CD86 in non-activated state. Induction of CD86 expression by stimulation of U937 cells with IFN-gamma revealed the presence of two functional GAS (gamma-interferon activation site) elements. Gel mobility shift assays showed that these two GAS elements specifically bind an IFN-gamma-induced transcriptional complex. The DNA-protein complex was supershifted by antibody to Stat1 alpha (signal transducer and activator of transcription), but not by antibodies to Stat 2, Stat 3 and Sp1, indicating that GAS elements interact with Stat1 alpha. Point mutations in the GAS elements prevented the formation of DNA-protein complex and significantly reduced the responsiveness of the reporter gene to IFN-gamma. These findings suggest that two functional GAS elements within the human CD86 promoter play an important role in the induction of CD86 gene by binding to IFN-gamma-induced Stat1 alpha.

T Suppressor Lymphocytes Inhibit NF-κB-Mediated Transcription of CD86 Gene in APC

CD8+CD28− human T suppressor cells (Ts) act on APC, inhibiting their ability to elicit Th activation and proliferation. This effect is due to inhibition of the CD40 pathway which normally leads to CD80 and CD86 up-regulation. To determine whether Ts inhibit expression of B7 molecules by blocking transcription, we cloned and characterized the CD86 promoter. Mutational analysis revealed that Ts inhibit transcription driven by the CD86 promoter. The NF-κB binding site, at −612 of the CD86 promoter, is essential for Th-induced transcription. In cultures containing Th and Ts, Ts inhibit Th-induced NF-κB activation in APC. Together, these findings indicate that Ts inhibition of NF-κB activation in APC is a means by which they regulate the activation and proliferation of Th.

Cross-Linking of Membrane CD43 Mediates Dendritic Cell Maturation

CD43/leukosialin is a major sialoglycoprotein of the dendritic cell (DC) surface, which can regulate cell adhesion and has the potential to mediate cell activation signals. Monocyte-derived DC transiently incubated with the anti-CD43 mAb, MEM-59, or with F(ab′)2 fragments, but not with monovalent Fab fragments or control IgG, 24 h later showed increased levels of membrane HLA-DR, CD54, CD40, CD80, CD86, and CD83. In parallel, CD43 cross-linking induced synthesis and release of IL-1β, IL-6, TNF-α, IL-12, and IL-10. CD43 ligation inhibited the endocytic activity of DC, and enhanced the capacity of DC to stimulate T cell proliferation in the primary allogeneic and autologous MLR assay. In addition, anti-CD43-treated DC were less efficient at presenting native HIV-1 reverse transcriptase to a specific CD4+ T cell clone, whereas presentation of the reverse transcriptase 55–72 peptide to the same clone was increased. Finally, MEM-59 or its F(ab′)2 fragments elicited a rise in intracellular free calcium and tyrosine phosphorylation of a 25-kDa protein in DC. The results thus indicate that CD43 cross-linking with specific ligands induces activation and functional maturation of DC.