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PubMed1985

Graft rejection in a congenic panel of rats with defined immune response genes for MHC class I antigens. I. Rejection of and priming to the RT1Aa antigen.

Allograft rejection in the rat has been shown to be under stringent immune response (Ir) gene control using major histocompatibility complex recombinant animals as donors. Presentation of an isolated class I antigenic difference to high responder recipients results in rapid graft rejection, but low responders fail to reject. This striking qualitative difference is also seen in some liver grafting experiments in which the donor presents a full MHC haplotype and minor antigen mismatch to the responders. Grafts of other organs, however, do not discriminate qualitatively between high and low responders when a full haplotype mismatch exists. We have used the canonical high and low-responder animals, (PVG X PVG-RT1u)F1 and PVG to examine whether any qualitative difference in responsiveness can be detected against the a haplotype using a variety of organ grafts. We have confirmed a qualitative difference between high and low responders using PVG.R1 donors presenting an isolated class I (Aa) difference. Rapid rejection by high responders contrasted with complete failure to reject by the low responders. No difference in rejection tempo was found when a full a haplotype mismatch was introduced. This could have reflected vigorous responses to I and C region differences, because rapid rejection through these regions was demonstrated using the PVG.r1 (AaIcCc) and PVG.r8 (AaIuCu) recombinants. The feeble immunogenicity of the Aa antigen for PVG animals was revealed by priming and cross-priming experiments showing not only that r1 failed to prime for subsequent r1 graft rejection, but that the Aa antigen presented in concert with Ia and Ca also failed to prime. An unexpected result was that the Aa antigen of r1 actually suppressed responsiveness, especially when delivered by a heart graft. This suppression not only extended to subsequent r1 grafts (for example, skin rafts) but also to subsequent grafts of a tissue. The mechanism of this suppression remains unclear but preliminary experiments argue in favor of enhancement rather than active suppression.

Animals↗
PubMed1993

Genetic control of the cellular in vitro response to the H-Y antigen in the rat.

The immune response against the male-specific H-Y antigen has been studied in RT1 congenic rat strains by assaying the cytotoxic and proliferative response in vitro after in vivo priming. The capacity to respond is associated with the RT1a and RT1n major histocompatibility haplotypes, and nonresponsiveness with the RT1u haplotype. Both, genes of the RT1.A region, which encodes class I antigens, and of the RT1.B/D region, which includes class II and transporter genes, are involved in the genetic control. In F1 hybrids haplotype preference of H-Y restriction occurs in favor of RT1a. Cross-priming can be induced in F1 hybrids by parental cells for RT1a-restricted cytotoxic and proliferative T cells. Allopriming is successful only in the RT1a-carrying strain, whereas xenopriming with mouse cells could not be elicited. The results are discussed in the context of current views on processing and presentation of antigens, and their relevance for transplantation is pointed out.

Animals↗
PubMed1998

Microchimerism after liver transplantation: prevalence and methodological aspects of detection.

BACKGROUND: Microchimerism after liver transplantation is a readily observed phenomenon. The immunological implications, however, remain unclear. Moreover, methodological approaches and their detection limits in the study of allogeneic microchimerism have not been studied in detail. METHODS: Therefore, the aim of this study was to evaluate the single-step and nested formats of the polymerase chain reaction/sequence-specific priming (PCR-SSP) approach under standardized conditions. For that purpose, a panel of recombinant plasmid clones was generated by PCR cloning. The panel contained the allelic sequences of the second exon of DRB1 covering all DR specificities on a low-resolution level. Using this panel, limiting dilution assays for various DR sequences in the presence and absence of competitor DNA were carried out to determine the minimal number of copies required for detection by single-step and nested PCR-SSP. Subsequently, 22 liver transplant recipients were analyzed in a retrospective study for the presence of allogeneic microchimerism by nested PCR-SSP. RESULTS: Although at least 10 copies of template DNA could be detected by nested PCR-SSP overall, single-step PCR-SSP was on average 10(2) to 10(3) times less sensitive. Upon the addition of human competitor DNA, the detection limits decreased on average by a factor of 10. In addition, sequence-specific differences in amplification efficiency could be appreciated. Using nested PCR-SSP, peripheral blood allogeneic microchimerism could be observed in 17 of 22 HLA-DR-mismatched liver recipients. Recombinants representing recipient DRB1 specificities were used to exclude false-positive results by lack of cross-reactivities of the donor-specific primers and to evaluate negative results due to sample-related reduced amplification efficiencies in microchimerism-negative recipients. In donor/recipient combinations that differed by at least one DR specificity, allogeneic microchimerism was seen in 87.5% of the cases. In five chimerism-negative cases, sample-related problems were detected in two cases. CONCLUSION: The optimization and standardization of the detection of genomic HLA sequences at low copy number may be greatly facilitated using a clonal reference system. Furthermore, a clonal reference system may be used to conduct cross-priming experiments to exclude false-positive results and may allow the determination of sample-specific detection limits for donor-derived HLA-DR specificities in chimerism-negative patients. Our evaluation of the PCR-SSP approach for the study of allogeneic microchimerism indicated that nested PCR-SSP provides the most sensitive format when HLA sequences are targeted. Yet, the detection sensitivity may vary between individual alleles and specificities. Allogeneic microchimerism in liver recipients can be observed in the majority of patients. However, the detection may be subject to the degree of mismatching, the HLA-DR alleles involved, and sample-related impaired PCR amplification efficiency.

Alleles↗
PubMed1995

A mechanism for the specific immunogenicity of heat shock protein-chaperoned peptides.

Endogenously synthesized antigenic determinants are generally presented on major histocompatibility complex (MHC) class I molecules, whereas exogenous determinants are presented by MHC class II molecules. Here, it is shown that exogenous antigens chaperoned by a heat shock protein can be channeled into the endogenous pathway, presented by MHC class I molecules, and recognized by CD8+ T lymphocytes. This pathway is functional only in a subset of macrophages among the cell types tested. These observations provide a basis for the tumor-specific and virus-specific immunogenicity of cognate heat shock protein preparations and offer a mechanism for the classical phenomenon of cross-priming.

Amino Acid Sequence↗
PubMed1996

Dominance of conserved B-cell epitopes of the Plasmodium falciparum merozoite surface protein, MSP1, in blood-stage infections of naive Aotus monkeys.

We have shown that conserved B epitopes were immunodominant in animals hyperimmunized with parasite-purified or recombinant merozoite surface protein MSP1 of Plasmodium falciparum. Cross-priming studies also suggested that a conserved T-helper epitope(s) is efficient in inducing the anti-MSP1 antibody response. In this study, we determined whether a similar profile of immune responses was induced during live P. falciparum infections. Naive Aotus monkeys were infected by blood-stage challenge with either one of the two dimorphic MSP1 alleles represented by the FUP and FVO parasites. Sera collected after parasite clearance were analyzed by enzyme-linked immunosorbent assays (ELISAs). Monkeys infected with parasites carrying one allelic form of MSP1 had antibodies that were equally reactive with homologous or heterologous MSP1s. This preferential recognition of conserved epitopes of MSP1 was confirmed by competitive binding ELISAs. Studies with Plasmodium yoelii and P. falciparum show that the C-terminal 19-kDa fragment of MSP1, MSP1(19), is the target of protective immunity. Thus, monkey sera were assayed for recognition with recombinant MSP1(19)s expressing variant and conserved B epitopes. Results of direct and competitive binding ELISAs showed that the anti-MSP1(19) antibodies were also directed primarily against conserved determinants. The similarities between vaccine- or infection-induced antibody responses suggest a possible reciprocal enhancement of the two populations of anti-MSP1 antibodies when a subunit MSP1 vaccine is introduced into populations living in areas where malaria is endemic. This together with previous observations that conserved determinants are important in MSP1-mediated immunity provides an optimistic outlook that a subunit MSP1 vaccine may be effective and practical for field applications in malaria-exposed populations.

Alleles↗
PubMed1991

Major histocompatibility complex restriction of T-cell responses to varicella-zoster virus in guinea pigs.

Varicella-zoster virus (VZV), adapted to grow in guinea pig fibroblasts, was injected subcutaneously into Hartley, strain 2, and strain 13 guinea pigs. Serum immunoglobulin G antibodies were detected 2 weeks later, and T-cell proliferative responses by blood lymphocytes were found 3 weeks after injection. The proliferating cells bound the 155 antibody, which defines a CD4-like subset of guinea pig T lymphocytes. VZV-infected fibroblasts of human, Hartley, and strain 13 origin elicited equivalent amounts of proliferation, which was quantitatively greater than that obtained with an extracted VZV antigen. Uninfected (control) human or guinea pig fibroblasts did not elicit T-cell proliferation. The proliferative response to VZV required the presence of autologous (strain 2 or 13) antigen-presenting cells and was blocked by the addition of an anti-class II major histocompatibility complex antibody. Effector cells obtained from in vitro cultures mediated class II-restricted cytotoxicity to L2C cells incubated with VZV. Class I-restricted responses were obtained only by cross-priming strain 2 animals with strain 13 peritoneal exudate cells which had been preincubated with VZV. The data indicate that guinea pigs resemble humans in that class II-restricted T cells with specificity for VZV are more readily cultured from blood than are class I-restricted cells.

Animals↗
PubMed2001

Using recombinant coxsackievirus B3 to evaluate the induction and protective efficacy of CD8+ T cells during picornavirus infection.

Coxsackievirus B3 (CVB3) is a common human pathogen that has been associated with serious diseases including myocarditis and pancreatitis. To better understand the effect of cytotoxic T-lymphocyte (CTL) responses in controlling CVB3 infection, we have inserted well-characterized CTL epitopes into the CVB3 genome. Constructs were made by placing the epitope of interest upstream of the open reading frame encoding the CVB3 polyprotein, separated by a poly-glycine linker and an artificial 3Cpro/3CDpro cleavage site. This strategy results in the foreign protein being translated at the amino- terminus of the viral polyprotein, from which it is cleaved prior to viral assembly. In this study, we cloned major histocompatibility complex class I-restricted CTL epitopes from lymphocytic choriomeningitis virus (LCMV) into recombinant CVB3 (rCVB3). In vitro, rCVB3 growth kinetics showed a 1- to 2-h lag period before exponential growth was initiated, and peak titers were approximately 1 log unit lower than for wild-type virus. rCVB3 replicated to high titers in vivo and caused severe pancreatitis but minimal myocarditis. Despite the high virus titers, rCVB3 infection of naive mice failed to induce a strong CD8+ T-cell response to the encoded epitope; this has implications for the proposed role of "cross-priming" during virus infection and for the utility of recombinant picornaviruses as vaccine vectors. In contrast, rCVB3 infection of LCMV-immune mice resulted in direct ex vivo cytotoxic activity against target cells coated with the epitope peptide, demonstrating that the rCVB3-encoded LCMV-specific epitope was expressed and presented in vivo. The preexisting CD8+ memory T cells could limit rCVB replication; compared to naive mice, infection of LCMV-immune mice with rCVB3 resulted in approximately 50-fold-lower virus titers in the heart and approximately 6-fold-lower virus titers in the pancreas. Although the inserted CTL epitope was retained by rCVB3 through several passages in tissue culture, it was lost in an organ-specific manner in vivo; a substantial proportion of viruses from the pancreas retained the insert, compared to only 0 to 1.8% of myocardial viruses. Together, these results show that expression of heterologous viral proteins by recombinant CVB3 provides a useful model for determining the mechanisms underlying the immune response to this viral pathogen.

Amino Acid Sequence↗
PubMed2001

Cross-presentation, dendritic cells, tolerance and immunity.

This review examines the role of cross-presentation in tolerance and immunity. We discuss (a) the antigenic requirements for cross-presentation, (b) the phenotype of the antigen presenting cell (APC), (c) the cellular interactions and molecular signals involved in cross-priming, and (d) the factors that direct the immune system toward tolerance or immunity. A large part of this review is dedicated to summarizing our current knowledge of the cross-presenting APC.

Animals↗
PubMed2000

Tumor-specific CD4+ T lymphocytes from cancer patients are required for optimal induction of cytotoxic T cells against the autologous tumor.

This study focuses on the specific CD4+ T cell requirement for optimal induction of cytotoxicity against MHC class II negative autologous tumors (AuTu) collected from patients with various types of cancer at advanced stages. CD4+ T cells were induced in cultures of cancer patients' malignant effusion-associated mononuclear cells with irradiated AuTu (mixed lymphocyte tumor cultures (MLTC)) in the presence of recombinant IL-2 and recombinant IL-7. Tumor-specific CD4+ T cells did not directly recognize the AuTu cells, but there was an MHC class II-restricted cross-priming by autologous dendritic cells (DCs), used as APC. CD8+ CTL, also induced during the MLTC, lysed specifically AuTu cells or DCs pulsed with AuTu peptide extracts (acid wash extracts (AWE)) in an MHC class I-restricted manner. Removal of CD4+ T cells or DCs from the MLTC drastically reduced the CD8+ CTL-mediated cytotoxic response against the AuTu. AWE-pulsed DCs preincubated with autologous CD4+ T cells were able, in the absence of CD4+ T cells, to stimulate CD8+ T cells to lyse autologous tumor targets. Such activated CD8+ T cells produced IL-2, IFN-gamma, TNF-alpha, and GM-CSF. The process of the activation of AWE-pulsed DCs by CD4+ T cells could be inhibited with anti-CD40 ligand mAb. Moreover, the role of CD4+ T cells in activating AWE-pulsed DCs was undertaken by anti-CD40 mAb. Our data demonstrate for the first time in patients with metastatic cancer the essential role of CD4+ Th cell-activated DCs for optimal CD8+ T cell-mediated killing of autologous tumors and provide the basis for the design of novel protocols in cellular adoptive immunotherapy of cancer, utilizing synthetic peptides capable of inducing T cell help in vivo.

Aged↗
PubMed2000

Divergent roles for CD4+ T cells in the priming and effector/memory phases of adoptive immunotherapy.

The requirement for CD4(+) Th cells in the cross-priming of antitumor CTL is well accepted in tumor immunology. Here we report that the requirement for T cell help can be replaced by local production of GM-CSF at the vaccine site. Experiments using mice in which CD4(+) T cells were eliminated, either by Ab depletion or by gene knockout of the MHC class II beta-chain (MHC II KO), revealed that priming of therapeutic CD8(+) effector T cells following vaccination with a GM-CSF-transduced B16BL6-D5 tumor cell line occurred independently of CD4(+) T cell help. The adoptive transfer of CD8(+) effector T cells, but not CD4(+) effector T cells, led to complete regression of pulmonary metastases. Regression of pulmonary metastases did not require either host T cells or NK cells. Transfer of CD8(+) effector T cells alone could cure wild-type animals of systemic tumor; the majority of tumor-bearing mice survived long term after treatment (>100 days). In contrast, adoptive transfer of CD8(+) T cells to tumor-bearing MHC II KO mice improved survival, but eventually all MHC II KO mice succumbed to metastatic disease. WT mice cured by adoptive transfer of CD8(+) T cells were resistant to tumor challenge. Resistance was mediated by CD8(+) T cells in mice at 50 days, while both CD4(+) and CD8(+) T cells were important for protection in mice challenged 150 days following adoptive transfer. Thus, in this tumor model CD4(+) Th cells are not required for the priming phase of CD8(+) effector T cells; however, they are critical for both the complete elimination of tumor and the maintenance of a long term protective antitumor memory response in vivo.

Adoptive Transfer↗
PubMed2001

Multiple antigen-specific processing pathways for activating naive CD8+ T cells in vivo.

Current knowledge of the processing of viral Ags into MHC class I-associated ligands is based almost completely on in vitro studies using nonprofessional APCs (pAPCs). This is two steps removed from real immune responses to pathogens and vaccines, in which pAPCs activate naive CD8(+) T cells in vivo. Rational vaccine design requires answers to numerous questions surrounding the function of pAPCs in vivo, including their abilities to process and present peptides derived from endogenous and exogenous viral Ags. In the present study, we characterize the in vivo dependence of Ag presentation on the expression of TAP by testing the immunogenicity of model Ags synthesized by recombinant vaccinia viruses in TAP1(-/-) mice. We show that the efficiency of TAP-independent presentation in vitro correlates with TAP-independent activation of naive T cells in vivo and provide the first in vivo evidence for proteolytic processing of antigenic peptides in the secretory pathway. There was, however, a clear exception to this correlation; although the presentation of the minimal SIINFEKL determinant from chicken egg OVA in vitro was strictly TAP dependent, it was presented in a TAP-independent manner in vivo. In vivo presentation of the same peptide from a fusion protein retained its TAP dependence. These results show that determinant-specific processing pathways exist in vivo for the generation of antiviral T cell responses. We present additional findings that point to cross-priming as the likely mechanism for these protein-specific differences.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Host B7-1 and B7-2 costimulatory molecules contribute to the eradication of B7-1-transfected P815 tumor cells via a CD8+ T cell-dependent mechanism.

B7-1 (CD80)-transfected P815 tumor cells were previously shown to elicit tumor-eradicating immunity that leads to the regression of B7-1+ P815 tumors after transient growth in normal syngeneic (DBA/2) mice. Here, we show that not only the B7-1 molecule but also the B7-2 (CD86) molecule contributed to the eradication of B7-1+ P815 tumors. The B7-1 molecule that contributed to the eradication of B7-1+ P815 tumors was expressed not only on the tumor cells but also on host APCs, including MAC-1+ cells. The B7-2 molecule that contributed to the eradication of B7-1+ P815 tumors was expressed only on host APCs, such as B220+ cells, and not on the tumor cells. In spite of the fact that B7-expressing host APCs contributed to the eradication of B7-1+ P815 tumors, only CD8+ T cells without help from CD4+ T cells were important for tumor eradication. Taken together, these findings indicate that in addition to the ability of B7-1-transfected tumor cells to stimulate CD8+ T cell-mediated tumor-eradicating immunity directly, such tumor cells can also stimulate CD8+ T cell-mediated tumor-eradicating immunity indirectly as a result of cross-priming through B7-expressing host APCs.

Animals↗
PubMed1999

Immunogenicity of apoptotic cells in vivo: role of antigen load, antigen-presenting cells, and cytokines.

Apoptosis allows the clearance of unwanted cells from living tissues without causing inflammation. Processing of phagocytosed apoptotic cells yields Ags that access the cytosol and the MHC class I pathway of engulfing cells and are recognized by Ag-specific CTL. We show here that injection of apoptotic RMA cells, a syngeneic T cell lymphoma, into C57BL/6 mice results in priming of a functional and long-lasting tumor-specific immune response. Cross-priming of CTLs by apoptotic cells requires CD4+ T cell help. Apoptotic cells, however, are at least 20-fold less immunogenic than nonreplicating live cells. Immunogenicity of apoptotic cells is proportional to the number of cells injected, correlates with the serum concentration of IL-10 and IL-1beta cytokines, and is enhanced in IL-10 knockout mice. Moreover, immunization with dendritic cells (DCs), but not macrophages (Mphi), pulsed with apoptotic cells primes tumor-specific CTLs and confers protection against a tumor challenge. Our findings demonstrate that tumor cells undergoing apoptosis are, though scarcely, immunogenic in vivo, outline the different roles of Mphi and DCs in the physiologic clearance of unwanted cells, and have implications in designing immunomodulating vaccines.

Adoptive Transfer↗
PubMed1999

Heat shock protein 70 induced during tumor cell killing induces Th1 cytokines and targets immature dendritic cell precursors to enhance antigen uptake.

Previously, we reported that killing tumor cells in vivo with the HSV thymidine kinase/ganciclovir system generates potent antitumor immunity, determined in part by the mechanism by which the cells die and by the levels of inducible heat shock protein (hsp) expression induced during the process of cell death. Here, we show that induction of hsp70 expression induces an infiltrate of T cells, macrophages, and predominantly dendritic cells (DCs) into the tumors as well as an intratumoral profile of Th1 cytokine expression (IFN-gamma, TNF-alpha, and IL-12) and enhances immunogenicity via a T cell-mediated mechanism. In addition, the protection conferred by hsp70 is both tumor and cell specific. We also demonstrate that hsp70 targets immature APC to make them significantly more able to capture Ags. This is likely to optimize cross-priming of the infiltrating APC with tumor Ags, which are simultaneously being released by the dying cells. In addition, using an Myc epitope-tagged hsp70 expression vector, we present evidence that hsp70 released from dying tumor cells is taken up directly into DCs and may, therefore, be involved in direct chaperoning of Ags into DCs. Taken together, our data suggest that hsp70 induction serves to signal the immune system of the presence of an immunologically relevant (dangerous) situation against which an immune reaction should be raised.

Animals↗
PubMed1999

MHC class I-restricted cytotoxic lymphocyte responses induced by enterotoxin-based mucosal adjuvants.

The ability of enterotoxin-based mucosal adjuvants to induce CD8+ MHC class I-restricted CTL responses to a codelivered bystander Ag was examined. Escherichia coli heat-labile toxin (LT), or derivatives of LT carrying mutations in the A subunit (LTR72, LTK63), were tested in parallel with cholera toxin (CT) or a fusion protein consisting of the A1 subunit of CT fused to the Ig binding domain of Staphylococcus aureus protein A (called CTA1-DD). Intranasal (i.n.) immunization of C57BL/6 mice with CT, CTA1-DD, LT, LTR72, LTK63, but not rLT-B, elicited MHC class I-restricted CD8+ T cell responses to coadministered OVA or the OVA CTL peptide SIINFEKL (OVA257-264). CT, LT, and LTR72 also induced CTL responses to OVA after s.c. or oral coimmunization whereas LTK63 only activated responses after s.c. coimmunization. rLT-B was unable to adjuvant CTL responses to OVA or OVA257-264 administered by any route. Mice treated with an anti-CD4 mAb to deplete CD4+ T cells mounted significant OVA-specific CTL responses after i.n. coadministration of LT with OVA or OVA257-264. Both 51Cr release assays and IFN-gamma enzyme-linked immunospot assays indicated that IFN-gamma-/- and IL-12 p40-/- gene knockout mice developed CTL responses equivalent to those detected in normal C57BL/6 mice. The results highlight the versatility of toxin-based adjuvants and suggest that LT potentiates CTL responses independently of IL-12 and IFN-gamma and probably by a mechanism unrelated to cross-priming.

Adenosine Diphosphate Ribose↗
PubMed1988

Genetic and stimulator cell requirements for generation and activation of minor histocompatibility antigen-specific memory cytotoxic T-lymphocyte precursors.

By adding IL-2 (supernatant of culture of concanavalin A-activated rat spleen cells) on Day 3 of mixed leucocyte cultures (MLC) we managed to fully activate multiple minor histocompatibility antigen (MIHA)-specific cytotoxic T-lymphocyte precursors (CTLp). In this newly developed system we studied genetic and stimulator cell requirements for the generation and activation of MIHA-specific memory CTLp. Memory CTLp were activated to generate effector CTL in MLC only when major histocompatibility complex (MHC)-compatible MIHA-allogeneic cells were used as stimulators. In contrast, memory CTLp were generated in mice that were primed by injection of either MHC-compatible or incompatible MIHA-allogeneic spleen cells. A surprisingly small number (10(4] of MHC-disparate cells cross-primed mice effectively. For priming, no special accessory cell types were required as stimulators, and 10(4) adherent cell-depleted spleen cells primed mice as well. These results contrasted to another finding that sonication-disrupted 10(6) stimulator cells did not prime mice effectively, and antigens shed from 10(7) live stimulator cells failed to sensitize host antigen-presenting cells for priming. It is suggested from these results that the mode of recognition of MIHA by virgin CTLp is unique or that an as yet unknown unusual stimulation pathway works for the priming.

Animals↗
PubMed1982

Effect of recent antigen exposure on the functional expression of B cell subpopulations.

We investigated whether the definition of functional B cell subpopulations changes after the exposure of B cells to specific antigen. Recent in vivo priming with fluorescein- (FL) coupled T-independent (TI) antigens leads to an augmentation of the subsequent in vitro responses of B cells to FL-coupled TI antigens, including FL-polymerized flagellin, FL-lipopolysaccharide, and FL-Brucella abortus, as well as a FL-coupled T-dependent (TD) antigen, FL-keyhole limpet hemocyanin (KLH). This effect, which is evident 7 days after priming, is of short duration in that B cells from FL-Ficoll injected mice display normal responsiveness 3 wk after priming. When mice are primed with FL-KLH, the TD antigen, B cells responsive to a subsequent FL-KLH challenge are expanded, but not short-term cross-priming for any of the TI antigen challenges is observed. Limiting dilution precursor analysis shows that B cell populations responding to different FL-coupled TD and TI antigens overlap in unimmunized animals. FL-TI antigen priming induces not only quantitative changes in the responding B cells (increased precursor frequencies) but also results in functional changes in FL-specific B cells. The primed B cells now respond to FL-hapten in a carrier-restricted manner and behave as independent (non-overlapping) subpopulations. We suggest that B cell responses to different forms of the same hapten are influenced in part by their recent "history" of antigenic exposure.

Animals↗
PubMed1997

Interleukin-10 prevents dendritic cell accumulation and vaccination with granulocyte-macrophage colony-stimulating factor gene-modified tumor cells.

A wide variety of human tumors express IL-10 for reasons poorly understood. We have analyzed the effect of spontaneous IL-10 expression by a mouse tumor (J558L) on its immunoparalyzing effect. Because "cross-priming" of T cells by host Ag-presenting cells for MHC class I-restricted tumor Ags is a major pathway for induction of tumor immunity and that is enhanced by granulocyte-macrophage (GM) CSF, we expressed this cytokine in J558L cells. GM-CSF-secreting cells were not effective when used for immunization against challenge with the parental tumor. Inhibition of IL-10 expression through an IL-10 antisense retrovirus restored the vaccine efficacy of GM-CSF-producing J558L cells, demonstrating a direct role of IL-10 in paralyzing the GM-CSF-induced antitumor immune response. Since the tumor used for challenge produced IL-10, we conclude that IL-10 interfered primarily with the initiation but not the effector phase of the immune response. Immunohistochemical analysis of the vaccine site showed a GM-CSF-induced accumulation of dendritic cells (DC) (MHC class II+ and DEC-205+) in the absence of IL-10. In the presence of IL-10, DC accumulation was completely inhibited. Together, our results demonstrate an antagonistic effect of IL-10 with respect to GM-CSF-induced DC accumulation and tumor immunity and suggest a new mechanism by which tumors escape immune recognition: namely by preventing APC from obtaining access to tumor Ags.

Animals↗