Inhibition Of Antigen Presentation Research Articles

Antigen presentation under the influence of ‘immune evasion’ proteins and its modulation by interferon-gamma: implications for immunotherapy of cytomegalovirus infection with antiviral CD8 T cells

Cytomegalovirus (CMV) disease with multiple organ manifestations is the most feared viral complication limiting the success of hematopoietic cell transplantation as a therapy of hematopoietic malignancies. A timely endogenous reconstitution of CD8 T cells controls CMV infection, and adoptive transfer of antiviral CD8 T cells is a therapeutic option to prevent CMV disease by bridging the gap between an early CMV reactivation and delayed endogenous reconstitution of protective immunity. Preclinical research in murine models has provided 'proof of concept' for CD8 T-cell therapy of CMV disease. Protection by CD8 T cells appears to be in conflict with the finding that CMVs encode proteins that inhibit antigen presentation to CD8 T cells by interfering with the constitutive trafficking of peptide-loaded MHC class I molecules (pMHC-I complexes) to the cell surface. Here, we have systematically explored antigen presentation in the presence of the three currently noted immune evasion proteins of murine CMV in all possible combinations and its modulation by pre-treatment of cells with interferon-gamma (IFN-γ). The data reveal improvement in antigen processing by pre-treatment with IFN-γ can almost overrule the inhibitory function of immune evasion molecules in terms of pMHC-I expression levels capable of triggering most of the specific CD8 T cells, though the intensity of stimulation did not retrieve their full functional capacity. Notably, an in vivo conditioning of host tissue cells with IFN-γ in adoptive cell transfer recipients constitutively overexpressing IFN-γ (B6-SAP-IFN-γ mice) enhanced the antiviral efficiency of CD8 T cells in this transgenic cytoimmunotherapy model.

HDL and adaptive immunity: A tale of lipid rafts

Lipid rafts are membrane microdomains enriched with cholesterol, sphingolipids and proteins associated with several relevant biological processes, including signaling, protein transport, adhesion. The functional properties of lipid rafts are strictly depending upon their lipid composition; cholesterol depletion from these microdomains downregulates signaling pathways in several cells, including immune cells and disturb antigen-presenting ability [ [1] Anderson H.A. Hiltbold E.M. Roche P.A. Concentration of MHC class II molecules in lipid rafts facilitates antigen presentation. Nat Immunol. 2000; 1: 156-162 Crossref PubMed Scopus (298) Google Scholar ]. In fact, MHC class II molecules, that play a role in antigen presentation and signal transduction, localize in lipid-rich microdomains in antigen presenting cells (APCs) [ [2] Norata G.D. Pirillo A. Ammirati E. Catapano A.L. Emerging role of high density lipoproteins as a player in the immune system. Atherosclerosis. 2012; 220: 11-21 Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar ]. The number of MHC class II molecules present on the surface of APCs are crucial for the activation of T cells; lipid rafts concentrate MHC-peptide complex on APCs surface, decreasing the amount of antigen required for T cell activation [ [3] Zilber M.T. Setterblad N. Vasselon T. et al. MHC class II/CD38/CD9: a lipid-raft-dependent signaling complex in human monocytes. Blood. 2005; 106: 3074-3081 Crossref PubMed Scopus (74) Google Scholar ]. HDL and ApoA-I inhibit antigen presentation-mediated T cell activation by disrupting lipid rafts in antigen presenting cellsAtherosclerosisVol. 225Issue 1PreviewDepletion of cholesterol by methyl-β-cyclodextrin (MCD) on peptide-loaded antigen presenting cells (APCs) inhibits antigen presentation and T cell activation. However, whether membrane cholesterol efflux induced by high-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I) also results in inhibition of antigen presentation and T cell activation is still unknown. Full-Text PDF

HDL and ApoA-I inhibit antigen presentation-mediated T cell activation by disrupting lipid rafts in antigen presenting cells

ObjectiveDepletion of cholesterol by methyl-β-cyclodextrin (MCD) on peptide-loaded antigen presenting cells (APCs) inhibits antigen presentation and T cell activation. However, whether membrane cholesterol efflux induced by high-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I) also results in inhibition of antigen presentation and T cell activation is still unknown. Methods and resultsVarious types of APCs, including B cells, macrophages and dendritic cells (DCs), were first loaded with antigen, then incubated with HDL and apoA-I to decrease cellular membrane cholesterol content. After being treated with HDL and apoA-I, APCs demonstrated decreased potential to activate T cells, and this decrease correlated with an increase in cholesterol efflux from APCs. Cholesterol repletion reversed the inhibitory effects of HDL and apoA-I, demonstrating that the observed reduction in T cell proliferation is mediated through cholesterol. Furthermore, lipid raft analysis showed that HDL and apoA-I reduced cholesterol and major histocompatibility (MHC) class II protein content in lipid rafts, suggesting that cholesterol efflux from APCs to HDL and apoA-I inhibits antigen presentation and T cell activation by reducing lipid rafts assembly in APCs. ConclusionHDL and apoA-I inhibit the capacity of APCs to stimulate T cell activation, and this inhibition can be attributed to cholesterol efflux and the ensuing disruption of plasma membrane lipid rafts in APCs. Overall, these findings suggest that cholesterol efflux mediated by HDL and apoA-I may serve to link immunity and cardioprotection.

Structural basis of evasion of cellular adaptive immunity by HIV-1 Nef

The HIV-1 protein Nef inhibits antigen presentation by class I major histocompatibility complex (MHC-I). We determined the mechanism of this activity by solving the crystal structure of a protein complex comprising Nef, the MHC-I cytoplasmic domain (MHC-I CD) and the μ1 subunit of the clathrin adaptor protein complex 1. A ternary, cooperative interaction clamps the MHC-I CD into a narrow binding groove at the Nef-μ1 interface, which encompasses the cargo-recognition site of μ1 and the proline-rich strand of Nef. The Nef C terminus induces a previously unobserved conformational change in μ1, whereas the N terminus binds the Nef core to position it optimally for complex formation. Positively charged patches on μ1 recognize acidic clusters in Nef and MHC-I. The structure shows how Nef functions as a clathrin-associated sorting protein to alter the specificity of host membrane trafficking and enable viral evasion of adaptive immunity.

Suppression of antigen presentation by the adenovirus E3-19K protein; a crystallographic analysis of E3-19K/MHC I interaction (106.37)

Abstract The cell-surface presentation of viral antigens by MHC class I molecules is critical for eliminating infected cells. In turn, viruses have evolved strategies to interfere with the process of antigen presentation. The adenovirus (Ad) E3-19K protein binds to and retains MHC class I molecules in the endoplasmic reticulum (ER), blocking their egress to the cell surface. We characterized for the first time interaction between Ad type 2 (Ad2) E3-19K and HLA-A2 using x-ray crystallography. Our structure to 2.1Å resolution reveals that Ad2 E3-19K interacts with the N-terminus of the α1-helix and C-terminus of the α2-helix of HLA-A2, i.e., the C-terminal end of the groove. E3-19K binds away from the opening of the groove. This mode of binding is entirely consistent with our biochemical studies of E3-19K/MHC I interaction, including the ability of E3-19K to associate with mature and immature MHC class I molecules. Importantly, the Ad2 E3-19K/HLA-A2 structure reveals how E3-19K uses it variable and conserved regions to bind to MHC I, and how it accommodates polymorphism in MHC I. Our structure also allows to understand the ability of E3-19K of different Ad serotypes and subgroups to associate with MHC I in an allele- and locus-specific manner. Overall, the Ad2 E3-19K/HLA-A2 structure reveals determinants in E3-19K that are critical for targeting MHC class I molecules. It also permits to better understand how E3-19K has evolved to subvert antigen presentation.

Suppression of antigen presentation by the adenovirus E3-19 K protein; a crystallographic analysis of E3-19 K/MHC I interaction

Suppression of antigen presentation by the adenovirus E3-19 K protein; a crystallographic analysis of E3-19 K/MHC I interaction

Green tea consumption: an alternative approach to managing oral lichen planus

Oral lichen planus (OLP) is a T-cell-mediated inflammatory autoimmune disease, whose pathogenesis includes both antigen-specific and non-specific mechanisms. Antigen-specific mechanisms in OLP consist of antigen presentation, lymphocyte activation, proliferation and migration as well as keratinocyte apoptosis mediated by CD8(+) cytotoxic T-cells, whereas non-specific mechanisms include mast cell degranulation and matrix metalloproteinase (MMP) activation in OLP lesions. Deficient antigen-specific transforming growth factor-β (TGF-β)-mediated immunosuppression may also contribute to the pathogenesis of OLP. In addition, OLP is considered to be a potentially malignant disorder with a malignant transformation rate of 0-5.3%. Green tea, especially epigallocatechin-3-gallate, possesses anti-inflammatory and chemopreventive properties. It can inhibit antigen presentation, T-cell activation, proliferation and migration, keratinocyte apoptosis, nuclear factor-kappaB (NF-кB) activation and MMP-9 activity, as well as regulated on activation, normal T-cell expressed and secreted (RANTES) expression, and can modulate the imbalance between TGF-β and interferon-γ signaling, all of which are involved in the pathogenesis of OLP. Thus, our hypothesis is that green tea consumption may decrease OLP incidence and provide a neoteric, nontoxic and inexpensive therapeutic strategy for OLP. Furthermore, green tea might be a possible agent for preventing malignancies in OLP.

Effect of oestradiol and pathogen‐associated molecular patterns on class II‐mediated antigen presentation and immunomodulatory molecule expression in the mouse female reproductive tract

Cells of the female reproductive tract (FRT) can present antigen to naive and memory T cells. However, the effects of oestrogen, known to modulate immune responses, on antigen presentation in the FRT remain undefined. In the present study, DO11.10 T-cell antigen receptor transgenic mice specific for the class II MHC-restricted ovalbumin (OVA) 323-339 peptide were used to study the effects of oestradiol and pathogen-associated molecular patterns on antigen presentation in the FRT. We report here that oestradiol inhibited antigen presentation of OVA by uterine epithelial cells, uterine stromal cells and vaginal cells to OVA-specific memory T cells. When ovariectomized animals were treated with oestradiol for 1 or 3 days, antigen presentation was decreased by 20-80%. In contrast, incubation with PAMP increased antigen presentation by epithelial cells (Pam(3)Cys), stromal cells (peptidoglycan, Pam(3)Cys) and vaginal cells (Pam(3)Cys). In contrast, CpG inhibited both stromal and vaginal cell antigen presentation. Analysis of mRNA expression by reverse transcription PCR indicated that oestradiol inhibited CD40, CD80 and class II in the uterus and CD40, CD86 and class II in the vagina. Expression in isolated uterine and vaginal cells paralleled that seen in whole tissues. In contrast, oestradiol increased polymeric immunoglobulin receptor mRNA expression in the uterus and decreased it in the vagina. These results indicate that antigen-presenting cells in the uterus and vagina are responsive to oestradiol, which inhibits antigen presentation and co-stimulatory molecule expression. Further, these findings suggest that antigen-presenting cells in the uterus and vagina respond to selected Toll-like receptor agonists with altered antigen presentation.

AKAPs in lipid rafts are required for optimal antigen presentation by dendritic cells

Dendritic cell (DC) maturation and antigen presentation are regulated by activation of protein kinase A (PKA) signaling pathways, through unknown mechanisms. We have recently shown that interfering with PKA signaling through the use of anchoring inhibitor peptides hinders antigen presentation and DC maturation. These experiments provide evidence that DC maturation and antigen presentation are regulated by A-kinase anchoring proteins (AKAPs). Herein, we determine that the presence of AKAPs and PKA in lipid rafts regulates antigen presentation. Using a combination of western blotting and immuno-cytochemistry, we illustrate the presence of AKAP149, AKAP79, Ezrin and the regulatory subunits of PKA in DC lipid rafts. Incubation of DCs with the type II anchoring inhibitor, AKAP-in silico (AKAP-IS), removes Ezrin and RII from the lipid raft without disrupting raft formation. Addition of a lipid raft disruptor, methyl-β-cyclodextrin, blocks the efficacy of AKAP-IS, suggesting that the lipid raft must be intact for AKAP-IS to inhibit antigen presentation. Ezrin and AKAP79 are present in the lipid raft of stimulated KG1 cells, but Ezrin is not present in the lipid raft of unstimulated KG1 cells and AKAP79 levels are greatly diminished, suggesting that Ezrin and AKAP79 may be the key AKAPs responsible for regulating antigen presentation.

Determinants of the endoplasmic reticulum (ER) lumenal-domain of the adenovirus serotype 2 E3-19K protein for association with and ER-retention of major histocompatibility complex class I molecules

The E3-19K immunomodulatory protein from adenoviruses (Ads) inhibits antigen presentation by major histocompatibility complex (MHC) class I molecules. As a result, the ability of Ad-specific cytotoxic T lymphocytes (CTLs) to lyse infected cells is suppressed. The ER-lumenal domain of E3-19K is subdivided into a variable (residues 1 to ∼78/81) and conserved (residues ∼79/82 to 98) region followed by a linker (residues 99–107). Using molecular and cellular approaches, we characterized in detail the properties of the ER-lumenal domain of E3-19K that enable it to target MHC class I molecules. Proteolysis of recombinant serotype 2 E3-19K (residues 1–100) (with six His residues) generated a large N-terminal (residues 1–88) and a small C-terminal fragment (residues 94–100) in solution. Neither of these fragments associates with HLA-A*1101 as shown by a native gel band-shift assay. In contrast, the N-terminal 1-93 residues of Ad2 E3-19K exhibited the same binding affinity to HLA-A*1101 as E3-19K. Using a site-directed mutational analysis and flow cytometry, we show that Tyr93, but not Tyr88, critically modulates the cell-surface expression of MHC class I molecules. Taken together, these results indicate that the sequence comprising residues 89–93 (M89SKQY93), and in particular Tyr93, in the conserved region of E3-19K is critical for its immunomodulatory function. Residues 89–93 likely form a linker or loop in E3-19K. Overall, our data provide novel insights into the structure of E3-19K and identify key determinants for association with and ER-retention of its cellular target protein. This knowledge is important for our understanding of the molecular basis of Ad pathogenesis.

Biology of interleukin-10

Interleukin (IL)-10 is the most important cytokine with anti-inflammatory properties besides TGF-β and IL-35. It is produced by activated immune cells, in particular monocytes/macrophages and T cell subsets including Tr1, Treg, and Th1 cells. IL-10 acts through a transmembrane receptor complex, which is composed of IL-10R1 and IL-10R2, and regulates the functions of many different immune cells. In monocytes/macrophages, IL-10 diminishes the production of inflammatory mediators and inhibits antigen presentation, although it enhances their uptake of antigens. Additionally, IL-10 plays an important role in the biology of B cells and T cells. The special physiological relevance of this cytokine lies in the prevention and limitation of over-whelming specific and unspecific immune reactions and, in consequence, of tissue damage. At the same time, IL-10 strengthens the “scavenger”-function and contributes to induced tolerance. This review provides an overview about the cellular sources, molecular mechanisms, effects, and biological role of IL-10.

Inhibition of antigen presentation and T cell costimulation blocks PTH‐induced bone loss

T cells are required for continuous parathyroid hormone (cPTH) treatment to induce bone loss as they sensitize stromal cells to PTH through CD40 ligand (CD40L), a surface molecule of activated T cells. Since CD40L expression is a feature of activated T cells, we investigated whether antigen (Ag)-mediated T cell activation is required for PTH to exert its catabolic activity. We report that inhibition of Ag presentation through silencing of either class I or class II MHC-T cell receptor (TCR) interaction prevents the cortical bone loss induced by in vivo cPTH treatment. We also show that the bone loss and the stimulation of bone resorption induced by cPTH treatment are prevented by CTLA4-Ig, an inhibitor of T cell costimulation approved for the treatment of rheumatoid arthritis. Since inhibition of antigen-driven T cell activation by blockade of either TCR signaling or T cell costimulation is sufficient to silence the catabolic activity of cPTH, antigen-presenting cells and T lymphocyte interactions therefore play a critical role in the mechanism of action of PTH.

Targeting siglec-E on murine dendritic cells inhibits antigen presentation and CD4 and CD8 t cell responses

Dendritic cells (DCs) are the most potent antigen presenting cells of the immune system. They are important regulators of immune responses by their capacity to induce tolerance or immunity, depending...

Proteasome Inhibitors Decrease AAV2 Capsid derived Peptide Epitope Presentation on MHC Class I Following Transduction

Adeno-associated viral (AAV) vectors are an extensively studied and highly used vector platform for gene therapy applications. We hypothesize that in the first clinical trial using AAV to treat hemophilia B, AAV capsid proteins were presented on the surface of transduced hepatocytes, resulting in clearance by antigen-specific CD8+ T cells and consequent loss of therapeutic transgene expression. It has been previously shown that proteasome inhibitors can have a dramatic effect on AAV transduction in vitro and in vivo. Here, we describe using the US Food and Drug Administration-approved proteasome inhibitor, bortezomib, to decrease capsid antigen presentation on hepatocytes in vitro, whereas at the same time, enhancing gene expression in vivo. Using an AAV capsid-specific T-cell reporter (TCR) line to analyze the effect of proteasome inhibitors on antigen presentation, we demonstrate capsid antigen presentation at low multiplicities of infection (MOIs), and inhibition of antigen presentation at pharmacologic levels of bortezomib. We also demonstrate that bortezomib can enhance Factor IX (FIX) expression from an AAV2 vector in mice, although the same effect was not observed for AAV8 vectors. A pharmacological agent that can enhance AAV transduction, decrease T-cell activation/proliferation, and decrease capsid antigen presentation would be a promising solution to obstacles to successful AAV-mediated, liver-directed gene transfer in humans.

Proteasome Inhibitors Decrease AAV2 Capsid-Derived Peptide Epitope Presentation On MHC Class I Following Transduction.

Abstract 695Adeno-associated viral (AAV) vectors are one of the most extensively studied and highly used vector platforms for gene therapy applications. We have recently provided evidence for AAV capsid-derived antigen presentation through MHC class I on the surface of AAV-transduced cells, supporting the hypothesis that in the first clinical trial using AAV to treat Hemophilia B, AAV capsid proteins were presented on the surface of transduced hepatocytes, resulting in clearance by antigen-specific CD8+ T cells and consequent loss of therapeutic transgene expression. Proteasome inhibitors are small molecule compounds that are able to specifically inhibit the activity of the proteasome, resulting in a buildup of ubiquitinated proteins, increased intracellular reactive oxygen species, and a general decrease in presentation of MHCI-peptide complexes. It has previously been shown that proteasome inhibitors can have a dramatic effect on AAV transduction in vitro and in vivo. Here we describe using the FDA approved proteasome inhibitor, bortezomib, to decrease capsid antigen presentation on hepatocytes in vitro, while at the same time, enhancing gene expression in vivo. Using an AAV capsid specific T cell reporter line to analyze effects of proteasome inhibitor on antigen presentation, we demonstrated capsid antigen presentation at low MOI's, as well as inhibition of antigen presentation at clinically relevant levels of bortezomib. We also demonstrate that bortezomib can enhance FIX expression from an AAV2 vector in C57Bl/6 mice, however does not appear to enhance expression of AAV8. Based on the data presented here, it appears as if future studies using proteasome inhibitors in large animal models may be warranted. A pharmacological agent that can enhance AAV transduction, decrease T-cell activation/proliferation, and decrease antigen presentation would be a promising solution to many of the obstacles to successful translation of AAV-mediated, liver-directed gene transfer to the clinic. Disclosures:No relevant conflicts of interest to declare.

Inhibition of immunological function mediated DNA damage of alveolar macrophages caused by cigarette smoke in mice

Exposure to cigarette smoke impairs the pulmonary immune system, including alveolar macrophage function, although the mechanisms by which this occurs are not fully elucidated. This study investigates the effect of cigarette smoke exposure on the antigen-presenting activity of alveolar macrophages, which is required for antigen-specific response to T cells. C57BL/6 mice were exposed to cigarette smoke for 10 days using a Hamburg II smoking machine, and alveolar macrophages were obtained by bronchoalveolar lavage. The antigen-presenting activity of alveolar macrophages was significantly inhibited in mice exposed to cigarette smoke compared with mice not exposed to cigarette smoke. Major histocompatibility complex class II cell surface molecule–positive cells, B7-1 molecule–positive cells, and interleukin-1β messenger RNA gene expression in alveolar macrophages were significantly decreased in mice exposed to cigarette smoke compared with mice not exposed to cigarette smoke. In contrast, DNA damage and generation of superoxide and hydrogen peroxide in alveolar macrophages were significantly increased by cigarette smoke exposure. These results suggest that inhibition of the antigen-presenting activity of alveolar macrophages may result from decreased expression of major histocompatibility complex class II and B7-1 molecules and interleukin-1β messenger RNA gene expression following cigarette smoke exposure. Furthermore, inhibition of antigen presentation in alveolar macrophage may result from DNA damage induced by excessive amounts of reactive oxygen species being generated by alveolar macrophages following cigarette smoke exposure. These findings suggest that cigarette smoke impairs the immunological function of alveolar macrophages and, as a result, increases the risk for pulmonary infection.

Coxsackievirus B3 Inhibits Antigen Presentation In Vivo, Exerting a Profound and Selective Effect on the MHC Class I Pathway

Many viruses encode proteins whose major function is to evade or disable the host T cell response. Nevertheless, most viruses are readily detected by host T cells, and induce relatively strong T cell responses. Herein, we employ transgenic CD4+ and CD8+ T cells as sensors to evaluate in vitro and in vivo antigen presentation by coxsackievirus B3 (CVB3), and we show that this virus almost completely inhibits antigen presentation via the MHC class I pathway, thereby evading CD8+ T cell immunity. In contrast, the presentation of CVB3-encoded MHC class II epitopes is relatively unencumbered, and CVB3 induces in vivo CD4+ T cell responses that are, by several criteria, phenotypically normal. The cells display an effector phenotype and mature into multi-functional CVB3-specific memory CD4+ T cells that expand dramatically following challenge infection and rapidly differentiate into secondary effector cells capable of secreting multiple cytokines. Our findings have implications for the efficiency of antigen cross-presentation during coxsackievirus infection.

Uncontrolled herpes simplex virus-1 replication due to type I IFN receptor deficiency results in selective destruction of lymphatic vessels and inhibition of antigen presentation

Uncontrolled herpes simplex virus-1 replication due to type I IFN receptor deficiency results in selective destruction of lymphatic vessels and inhibition of antigen presentation

Antigen Display, T-Cell Activation, and Immune Evasion during Acute and Chronic Ehrlichiosis

How spatial and temporal changes in major histocompatibility complex/peptide antigen presentation to CD4 T cells regulate CD4 T-cell responses during intracellular bacterial infections is relatively unexplored. We have shown that immunization with an ehrlichial outer membrane protein, OMP-19, protects mice against fatal ehrlichial challenge infection, and we identified a CD4 T-cell epitope (IA(b)/OMP-19(107-122)) that elicited CD4 T cells following either immunization or infection. Here, we have used an IA(b)/OMP-19(107-122)-specific T-cell line to monitor antigen display ex vivo during acute and chronic infection with Ehrlichia muris, a bacterium that establishes persistent infection in C57BL/6 mice. The display of IA(b)/OMP-19(107-122) by host antigen-presenting cells was detected by measuring intracellular gamma interferon (IFN-gamma) production by the T-cell line. After intravenous infection, antigen presentation was detected in the spleen, peritoneal exudate cells, and lymph nodes, although the kinetics of antigen display differed among the tissues. Antigen presentation and bacterial colonization were closely linked in each anatomical location, and there was a direct relationship between antigen display and CD4 T-cell effector function. Spleen and lymph node dendritic cells (DCs) were efficient presenters of IA(b)/OMP-19(107-122), demonstrating that DCs play an important role in ehrlichial infection and immunity. Chronic infection and antigen presentation occurred within the peritoneal cavity, even in the presence of highly activated CD4 T cells. These data indicated that the ehrlichiae maintain chronic infection not by inhibiting antigen presentation or T-cell activation but, in part, by avoiding signals mediated by activated T cells.

Leishmania majorPhosphoglycans Influence the Host Early Immune Response by Modulating Dendritic Cell Functions

The precise role of Leishmania glycoconjugate molecules including phosphoglycans (PGs) and lipophosphoglycan (LPG) on host cellular responses is still poorly defined. Here, we investigated the interaction of Leishmania major LPG2 null mutant (lpg2(-)), which lacks both PGs and LPG, with dendritic cells (DCs) and the subsequent early immune response in infected mice. Surprisingly, the absence of phosphoglycans did not influence expression pattern of major histocompatibility complex class II (MHC II), CD40, CD80, and CD86 on DCs in vitro and in vivo. However, lpg2(-) L. major induced significantly higher production of interleukin-12p40 (IL-12p40) by infected bone marrow-derived DCs (BMDCs) than wild-type (WT) parasites in vitro. Furthermore, the production of IL-12p40 by draining lymph node cells from lpg2(-) mutant-infected mice was higher than those from WT L. major-infected mice. In model antigen presentation experiments, DCs from lpg2(-) mutant-infected mice induced more gamma interferon (IFN-gamma) and IL-2 production by Leishmania-specific T cells than those from WT-infected mice. Lymphocytes isolated from mice infected for 3 days with lpg2(-) parasites produce similar levels of IFN-gamma, but significantly less IL-4 and IL-10 than WT controls. Decreased IL-4 production was also seen in another general PG-deficient mutant lacking the Golgi UDP-galactose transporters (lpg5A(-) lpg5B(-)), but not with the lpg1(-) mutant lacking only LPG, thereby implicating PGs generally in the reduction of IL-4 production. Thus, Leishmania PGs influence host early immune response by modulating DC functions in a way that inhibits antigen presentation and promotes early IL-4 response, and their absence may impact the balance between Th1 and Th2 responses.