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C P Larsen

Publications and source records attributed to C P Larsen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Aggressive skin allograft rejection in CD28-/- mice independent of the CD40/CD40L costimulatory pathway.

CD28-/- mice have been utilized to study the role of B7/CD28 and B7-CTLA4 interactions. There is evidence that CTLA4 ligation may be critical for tolerance induction. The aim of the current study is to further investigate rejection responses of CD28-/- mice and to define the role of B7-CTLA4 interactions in the absence of the CD40 and CD28 pathways. Balb/c skin allografts were transplanted onto C57BL/6 (B6) wild type or CD28-/- mice treated with anti-CD40L, CTLA4-Ig, or combination blockade. To investigate the cellular mechanism of rejection in CD28-/- recipients, mice were treated with anti-CD4 or anti-CD8 antibodies prior to treatment with costimulation blockade. The fluoroscein dye CFSE was utilized to study T cell expansion in vivo. Surprisingly, treatment of B6 CD28-/- mice with CTLA4-Ig alone (MST 12d), anti-CD40L alone (MST 13d), or combined blockade (MST 13d) had no effect on allograft survival compared to untreated B6 CD28 mice (MST 11d). CD28-/- recipients depleted of CD4+ cells and treated with CTLA4-Ig, anti-CD40L, or combination blockade also did not have prolonged survival compared with untreated mice (MST 10d). In contrast, CD28-/- recipients depleted of CD8+ cells had markedly prolonged allograft survival when treated with either anti-CD40L alone (MST 49d) or with combination blockade (MST 57d). Studies utilizing CFSE demonstrated that CD28-/- CD8+ T cells are not defective in in vivo proliferation responses compared with wild type CD8 cells. Thus, CD28-/- CD8+ T cells are responsible for aggressive rejection responses of CD28-/- mice independent of the CD40 pathway. In addition, CD40L blockade does not result in CD4+ T cell tolerance in CD28 recipients, despite an intact B7-CTLA4 pathway.

Abatacept↗
PubMed2001

Trimellitic anhydride-induced allergic response in the guinea pig lung involves antibody-dependent and -independent complement system activation.

Trimellitic anhydride (TMA) is one of many low molecular weight compounds known to cause occupational asthma. In our previous studies the TMA-induced allergic response in guinea pigs was attenuated by depletion of complement. Specifically, the leakage of red blood cells and infiltration of inflammatory cells into the lung after TMA challenge was significantly reduced. Thus, we hypothesize that in the presence of specific antibody, TMA activates the complement system and complement activation products play a role in mediating inflammatory cell infiltration into the lung and lung hemorrhage. Guinea pigs were sensitized by intradermal injection of TMA in corn oil. An increase in the complement activation product C3a was detected in bronchoalveolar lavage, but not in plasma, of both sensitized and nonsensitized guinea pigs after intratracheal challenge with TMA conjugated to GPSA (TMA-GPSA). In vitro experiments demonstrated that TMA-GPSA caused complement activation by antibody-dependent as well as antibody-independent pathways. In sensitized animals, TMA-GPSA challenge caused significant increases in eosinophils, neutrophils, and macrophages in lung, along with increases in red blood cells and protein in the airspace. The infiltration of eosinophils was unique in that the magnitude of the GPSA/TMA-GPSA effect was significantly different between nonsensitized and sensitized animals. C3a concentrations in BAL correlated with all measures of cell infiltration in sensitized animals, but not in nonsensitized animals. These data indicate that complement activation in the absence of antibody is not sufficient for the complete allergic response to occur. Both sensitization and the complement system are required for TMA-induced eosinophilia.

Allergens↗
PubMed2000

Genetic characterization of strain differences in the ability to mediate CD40/CD28-independent rejection of skin allografts.

Simultaneous blockade of the CD40 and CD28 T cell costimulatory pathways effectively promotes skin allograft survival in C3H/HeJ mice, extending median survival times (MSTs) beyond 100 days. This strategy is markedly less effective in C57BL/6 mice, with MSTs ranging between 20 and 30 days. In this study, we investigate the underlying genetic causes of these distinct phenotypes. Using H-2 congenic mice, we show that the genetic basis for the varied responses between these two strains is independent of the H-2 locus and T cell precursor frequency. C57BL/6 mice treated with costimulation blockade are able to generate allospecific CTL- and IFN-gamma-producing T cells within 3-4 wk posttransplant, whereas mice with a C3H background generate neither CTL- nor IFN-gamma-producing cells. Thus, differences appear to be in the generation of the immune response and not T cell homing. Strain differences in costimulation blockade-induced hyporesponsiveness persist in the absence of CD4(+) T cells, implying a direct effect on CD8(+) T cells. We demonstrate that genetic differences are important in cells of hemopoietic origin and that the costimulation blockade-resistant phenotype is dominant. Analysis of BXH recombinant inbred strains indicates that multiple loci contribute to the phenotype, and that the blockade resistance loci are preliminarily linked to 17 markers on four chromosomes. We conclude that strain variation in allograft MSTs following CD40/CD28 blockade results from the ability of CD8(+) T cells in some strains to use alternative modes of costimulation to mount an effective alloresponse.

Abatacept↗
PubMed2000

Analysis of expression and function of the costimulatory molecule 4-1BB in alloimmune responses.

BACKGROUND: 4-1BB (CD137) is a T cell costimulatory molecule that promotes T cell activation. In this study, we investigated the role of 4-1BB costimulation in allogeneic T cell responses. METHODS: Vascularized heart transplantation, allogeneic mixed leukocyte reaction (MLR), and graft versus host disease models were used to examine 4-1BB and 4-1BBL expression. In addition, agonistic anti-4-1BB antibodies were used in MLR to functionally analyze T cell responses. RESULTS: Using a heart transplant model, we found that 4-1BB and 4-1BBL transcripts were both expressed in rejecting cardiac grafts. In the allogeneic MLR, 4-1BB was expressed on both activated CD4 and CD8 T cells and 4-1BB was expressed on T cells after multiple cell divisions in vivo. Functionally, 4-1BB was a potent stimulator of proliferation, cytokine secretion, and CD25 expression by CD8 T cells, but 4-1BB signals had a weak effect on the proliferation of CD4 T cells. Because 4-1BB promoted the secretion of IL-2 and the expression of CD25 on CD8 T cells, we investigated whether IL-2 was the only factor whereby 4-1BB signals induced CD8 T cell proliferation. Although IL-2 was required for optimal CD8 T cell proliferation, 4-1BB also costimulated CD8 T cell proliferation independently of IL-2. CONCLUSIONS: This study demonstrates that 4-1BB is expressed on activated, maximally divided T cells and shows that 4-1BB promotes CD8 T cell proliferation by enhancing signals through the IL-2 receptor and by other mechanisms independent of the IL-2 pathway.

Animals↗
PubMed2000

Cutting edge: administration of anti-CD40 ligand and donor bone marrow leads to hemopoietic chimerism and donor-specific tolerance without cytoreductive conditioning.

Transplantation tolerance, defined as allograft acceptance by an immunocompetent recipient in the absence of long-term immunosuppression, has remained an elusive goal in clinical transplantation. Robust experimental tolerance induction strategies have in common methods to induce mixed hemopoietic chimerism. To date, however, chimerism induction across allogeneic barriers has required recipient conditioning with irradiation or cytoablative agents. In this paper we show that B6 recipients of fully allogeneic BALB/c skin grafts treated with repeated doses of donor bone marrow and anti-CD40 ligand (CD40L) develop durable (>300 days), readily detectable (6-12%) multilineage hemopoietic chimerism, indefinite allograft acceptance (>300 days), and donor-specific tolerance to secondary skin grafts. Analysis of the TCR repertoire of treated mice indicates that the underlying mechanisms of tolerance are in part mediated by deletion of donor-reactive T cells. These data demonstrate that durable hemopoietic chimerism and robust transplantation tolerance can be achieved without cytotoxic conditioning using a potentially clinically applicable regimen.

Animals↗
PubMed2000

Transplantation of the bone marrow microenvironment leads to hematopoietic chimerism without cytoreductive conditioning.

BACKGROUND: It has been hypothesized that regimens to induce transplantation tolerance and long-term hematopoietic chimerism require recipient conditioning with whole body irradiation or a cytoablative regimen to create space within the marrow microenvironment to permit pluripotent stem cell engraftment. The purpose of this study was to determine if transplantation of an intact bone marrow microenvironment in the form of a bone graft would permit stable hematopoietic stem cell engraftment, shape the repertoire of developing T cells, and induce donor-specific unresponsiveness in the absence of a conditioning regimen. METHODS: Fragments of femur were transplanted under the kidney capsule of recipient mice. At defined time points after bone graft transplantation recipients were assayed for chimerism, bone graft viability, and responses to donor and third party alloantigens in vitro and in vivo. RESULTS: In the absence of an immunological barrier, bone graft transplantation resulted in long-term multi-lineage hematopoietic chimerism in the peripheral blood. Nude bone graft transplantation into SCID recipients resulted in development of donor- derived T cells that underwent negative selection on bone graft derived I-E+ cells within the thymus. Across a fully allogeneic barrier in immunocompetent recipients treated with combined blockade of the CD40 and CD28 pathways bone graft transplantation resulted in long-term donor-specific hyporesponsiveness in vitro and acceptance of donor specific skin grafts. CONCLUSIONS: Transplantation of bone marrow in the form of a bone graft may facilitate the production of hematopoietic chimerism and lead to long-term donor-specific hyporesponsiveness in the absence of a cytoreductive conditioning regimen.

Animals↗
PubMed2000

Vigorous allograft rejection in the absence of danger.

Tolerance to self is a necessary attribute of the immune system. It is thought that most autoreactive T cells are deleted in the thymus during the process of negative selection. However, peripheral tolerance mechanisms also exist to prevent development of autoimmune diseases against peripheral self-Ags. It has been proposed that T cells develop tolerance to peripheral self-Ags encountered in the absence of inflammation or "danger" signals. We have used immunodeficient Rag 1-/- mice to study the response of T cells to neo-self peripheral Ags in the form of well-healed skin and vascularized cardiac allografts. In this paper we report that skin and cardiac allografts without evidence of inflammation are vigorously rejected by transferred T cells or when recipients are reconstituted with T cells at a physiologic rate by nude bone graft transplantation. These results provide new insights into the role of inflammation or "danger" in the initiation of T cell-dependent immune responses. These findings also have profound implications in organ transplantation and suggest that in the absence of central deletional tolerance, peripheral tolerance mechanisms are not sufficient to inhibit alloimmune responses even in the absence of inflammation or danger.

Adoptive Transfer↗
PubMed2000

4-1BB costimulation is required for protective anti-viral immunity after peptide vaccination.

Peptide vaccination induces T cell activation and cytotoxic T cell development. In an effort to understand what factors can improve immune responses to peptide vaccination, the role of 4-1BB (CD137) costimulation was examined, since 4-1BB has been shown to promote T cell responses in other systems. 4-1BBL-deficient (-/-) and wild-type (+/+) mice were immunized with a lipidated lymphocytic choriomeningitis virus (LCMV) peptide NP396-404. Analysis of peptide-specific responses early after immunization by CTL assay, intracellular IFN-gamma staining, and IFN-gamma enzyme-linked immunospot assay (ELISPOT) indicated that CD8 T cell responses were reduced 3- to 10-fold in the absence of 4-1BB costimulation. Moreover, when agonistic anti-4-1BB Ab was given, CD8 T cell responses in 4-1BBL-/- mice were augmented to levels similar to those in 4-1BBL+/+ mice. Two months after immunization, 4-1BBL+/+ mice still had epitope-specific cells and were protected against viral challenge, demonstrating that peptide vaccination can induce long-term protection. In fact, 70% of CD8 T cells were specific for the immunizing peptide after viral challenge, demonstrating that strong, epitope-specific CD8 T cell responses are generated after peptide vaccination. In contrast, peptide-immunized 4-1BBL-/- mice had fewer epitope-specific cells and were impaired in their ability to resolve the infection. These results show that immunization with a single LCMV peptide provides long term protection against LCMV infection and point to costimulatory molecules such as 4-1BB as important components for generating protective immunity after vaccination.

Animals↗
PubMed2000

The role of CD40L in T cell-dependent nitric oxide production by murine macrophages.

Upon activation, T cells express CD40L, a member of the TNF cytokine superfamily, which serves as a ligand for CD40 on antigen presenting cells, including dendritic cells, B cells, and macrophages. While initial studies on the function of CD40 focused its role in the regulation of B cell activation, more recent studies have indicated that CD40 ligation may be critical for the initiation of T cell-dependent macrophage activation, including stimulation of nitric oxide production. However, the relative contribution of the CD40 pathway in macrophage nitric oxide production during T-dependent immune responses remains unclear. We have found that while CD40 ligation of macrophages can stimulate nitric oxide production, disruption of CD40 signaling during a T cell-mediated alloimmune response has no appreciable effect on nitric oxide production. If the T cell alloimmune response is restricted to CD4 cells, CD40L blockade has only a minimal effect on nitric oxide production. Rather, IFNgamma, produced by alloactivated T cells, seems to be a necessary 'first' signal for nitric oxide production, while TNFalpha and CD40L each provide independent 'second' signals. Finally, we demonstrate that CD40L stimulates macrophage NO production independent from autocrine TNFalpha stimulation. These results suggest that macrophage nitric oxide production during a T-dependent immune response requires IFNgamma production by CD4 cells whereas TNFalpha and CD40L can each provide important functionally overlapping 'second' signals to costimulate nitric oxide production, though neither is required.

Animals↗
PubMed2000

Analysis of a single-center experience with mycophenolate mofetil based immunosuppression in renal transplantation.

PURPOSE: Acute rejection continues to be a major clinical issue in renal transplantation. Three large multicenter trials have demonstrated a 50% decline in biopsy-proven rejection when mycophenolate mofetil (MMF) was given to renal transplant recipients with corticosteroids and cyclosporine. The purpose of this study was to compare the 6-month outcome of renal transplant recipients using MMF and non-MMF based immunosuppression protocols over a 4-year period at a single center. METHODS: This retrospective study analyzed three patient groups defined by their immunosuppression protocol. The first group included patients who received a quadruple immunosuppression regimen of anti-lymphocyte induction (ATG), cyclosporine (CYA), azathioprine (AZA), and corticosteroids (CCS), and were transplanted between October 1993 and May 1995 (AZA group). The second group included patients who received a triple immunosuppression regimen of CYA, MMF, and CCS, and were transplanted between June 1995 and May 1996 (MMF group). The third group included patients who were transplanted between January 1997 and December 1997, and received an immunosuppression regimen of CYA and MMF with a reduced CCS dosing schema (reduced steroid group (RST)). Data were collected from a retrospective review of inpatient and outpatient clinical records. RESULTS: A total of 325 patients were included in the study (106 AZA, 106 MMF, 113 RST). The demographic characteristics of the three groups were similar; however, the mean donor age for the AZA group was 40+/-15.1 years versus 33+/-14.1 years and 34+/-13.1 years for the MMF and RST groups, respectively (p<0.043). The incidence of acute, biopsy-proven rejection at 6 months was significantly less in the MMF group when compared with the AZA group [16 (15.1%) versus 35 (33%) patients, p = 0.002]. However, the incidence of acute, biopsy-proven rejection in the RST group (35 patients, 31%) was similar to that of the AZA group. Kaplan-Meier estimates for the cumulative incidence of acute rejection demonstrated a significant difference between the MMF group and the other two groups (p = 0.0059). The AZA group had more severe rejection as demonstrated by the more frequent use of antilymphocyte therapy for rejection treatment (68.4% episodes) compared with the MMF (38.9%) and RST (47.6%) groups. After 6 months of follow-up, 11 patients had lost their grafts (8, AZA; 1, MMF; 2, RST). One patient died in each of the AZA and RST groups due to hemorrhage and a pulmonary embolus, respectively. Four AZA patients were diagnosed with a malignancy (three post-transplant lymphoproliferative disorder, one squamous skin cell carcinoma) compared with 2 MMF patients (prostate cancer, basal skin cell carcinoma) and no RST patients. Herpes zoster was the only infection that occurred more frequently in the MMF group (p = 0.03). No other differences in infection rates were noted among the three groups. The initial length of hospital stay declined significantly over the 4-year study period [11+/-4.3 d (AZA), 7.0+/-4.0 d (MMF), 6.2+/-3.3 d (RST), p<0.001]. Total number of hospital days for the first 6 months also followed a similar declining pattern. Despite using intravenous cyclosporine immediately post-transplant in the MMF and RST groups, the incidence of delayed graft function was similar among the three groups. Average serum creatinine at 1 month was significantly lower in the MMF group (p = 0.008), but no difference was noted at 3 and 6 months when compared with the AZA and RST groups. CONCLUSION: This retrospective analysis indicates that MMF is an effective immunosuppressant. Decreased length of stay and less steroid resistant rejections with MMF is favorable for decreased hospital costs. However, the rebound in rejection rate with the RST group suggests that further study is needed to define the optimal use of this agent in combination with others to maximize effectiveness and minimize negative side effects.

Adult↗
PubMed1999

4-1BB ligand, a member of the TNF family, is important for the generation of antiviral CD8 T cell responses.

4-1BB (CD137) is a costimulatory molecule expressed on activated T cells and interacts with 4-1BB ligand (4-1BBL) on APCs. To investigate the role of 4-1BB costimulation for the development of primary immune responses, 4-1BBL-deficient (4-1BBL-/-) mice were infected with lymphocytic choriomeningitis virus (LCMV). 4-1BBL-/- mice were able to generate CTL and eliminate acute LCMV infection with normal kinetics, but CD8 T cell expansion was 2- to 3-fold lower than in wild-type (+/+) mice. In the same mice, virus-specific CD4 Th and B cell responses were minimally affected, indicating that 4-1BB costimulation preferentially affects CD8 T cell responses. This result contrasts with our earlier work with CD40L-deficient (CD40L-/-) mice, in which the CD8 T cell response was unaffected and the CD4 T cell response was markedly impaired. When both 4-1BBL- and B7-dependent signals were absent, CD8 T cell expansion was further reduced, resulting in lower CTL activity and impairing their ability to clear LCMV. Altogether, these results indicate that T cells have distinct costimulatory requirements: optimal CD8 responses require 4-1BBL-dependent interactions, whereas CD4 responses are minimally affected by 4-1BB costimulation, but require CD40-CD40L and B7-dependent interactions.

4-1BB Ligand↗
PubMed1999

CD40-CD40 ligand costimulation is required for generating antiviral CD4 T cell responses but is dispensable for CD8 T cell responses.

This study documents a striking dichotomy between CD4 and CD8 T cells in terms of their requirements for CD40-CD40 ligand (CD40L) costimulation. CD40L-deficient (-/-) mice made potent virus-specific CD8 T cell responses to dominant as well as subdominant epitopes following infection with lymphocytic choriomeningitis virus. In contrast, in the very same mice, virus-specific CD4 T cell responses were severely compromised. There were 10-fold fewer virus-specific CD4 T cells in CD40L-/- mice compared with those in CD40L+/+ mice, and this inhibition was seen for both Th1 (IFN-gamma, IL-2) and Th2 (IL-4) responses. An in vivo functional consequence of this Th cell defect was the inability of CD40L-/- mice to control a chronic lymphocytic choriomeningitis virus infection. This study highlights the importance of CD40-CD40L interactions in generating virus-specific CD4 T cell responses and in resolving chronic viral infection.

Animals↗
PubMed1999

Asialo GM1(+) CD8(+) T cells play a critical role in costimulation blockade-resistant allograft rejection.

Simultaneous blockade of the CD40 and CD28 costimulatory pathways is an effective treatment strategy to promote allograft acceptance but does not lead to indefinite allograft survival. The immune mechanisms responsible for costimulation-independent rejection are not defined. Here we have studied the rejection responses of murine C57BL/6 recipients, which we show to be relatively resistant to inhibition by combined CD40/CD28 blockade. We demonstrate that asialo GM1(+) CD8(+) cells play a critical role in this costimulation blockade-resistant rejection. These results provide new insights into the costimulatory requirements for T-cell subsets and demonstrate for the first time that combined blockade of the CD40 and CD28 pathways does not adequately inhibit CD8-mediated skin allograft rejection. Furthermore, we provide evidence that asialo GM1 is a potentially important therapeutic target for CD8-dependent immune responses.

Animals↗
PubMed1998

The role of the CD40 pathway in alloantigen-induced hyporesponsiveness in vivo.

Resting B (rB) cells are known to be incompetent APCs in vitro, which alone can induce specific unresponsiveness to single minor histocompatibility (miH) Ags and, when combined with CD40 pathway blockade, can induce hyporesponsiveness to MHC molecules in vivo. Here we show that anti-CD40 ligand (CD40L) mAb does not prevent the expression of B7-2 on allogeneic rB cells in vivo but did prolong donor-specific cardiac allograft survival. Moreover, pretreatment with professional APCs combined with anti-CD40L mAb induced hyporesponsiveness to alloantigens in vivo. rB cells from CD40 knockout mice were unable to induce unresponsiveness, while graft prolongation was achieved in CD40L knockout recipients pretreated with wild-type rB cells. These data suggest that CD40-CD40L interactions in the recipient play a critical role in the induction of hyporesponsiveness to alloantigens in vivo and that the effect of the CD40 pathway may be independent of its effect on the B7 costimulatory pathway.

Abatacept↗
PubMed1998

Prolonged acceptance of concordant and discordant xenografts with combined CD40 and CD28 pathway blockade.

BACKGROUND: The prompt and vigorous immune response to xenogenic tissue remains a significant barrier to clinical xenotransplantation. Simultaneous blockade of the CD28 and CD40 costimulatory pathways has been shown to dramatically inhibit the immune response to alloantigen. METHODS: . In this study, we investigated the ability of simultaneous blockade of the CD28 and CD40 pathways to inhibit the immune response to xenoantigen in the rat-to-mouse and pig-to-mouse models. RESULTS: Simultaneous blockade of the CD28 and CD40 pathways produced marked inhibition of the cellular response to xenoantigen in vivo and produced long-term acceptance of xenogeneic cardiac and skin grafts (rat-to-mouse), and markedly suppressed an evoked antibody response to xenoantigen. In addition, this strategy significantly prolonged the survival of pig skin on recipient mice. CONCLUSIONS: Long-term hyporesponsiveness to xenoantigen across both a concordant and discordant species barrier, measured by the stringent criterion of skin grafting, can be achieved using a noncytoablative treatment regimen.

Abatacept↗
PubMed1998

IFN-gamma is critical for long-term allograft survival induced by blocking the CD28 and CD40 ligand T cell costimulation pathways.

It is postulated that IFN-gamma production hinders long-term acceptance of transplanted organs. To test this hypothesis, we compared survival of skin and heart allografts in wild-type (IFN-gamma+/+) mice to that in IFN-gamma gene knockout (IFN-gamma-/-) mice. We found that perioperative blockade of the CD28 and/or CD40 ligand T cell costimulation pathways induces long-term skin and heart allograft survival in IFN-gamma+/+ recipients but fails to do so in IFN-gamma-/- mice or in wild-type mice treated with IFN-gamma-neutralizing Ab at the time of transplantation. In vitro studies showed that endogenously produced IFN-gamma down-regulates T cell proliferation and CTL generation in MLCs. These actions of IFN-gamma were not mediated by TNF-alpha production or Fas-Fas ligand interactions. In vivo studies revealed exaggerated expansion and, subsequently, impaired deletion of superantigen-reactive T lymphocytes in IFN-gamma-/- mice injected with staphylococcal enterotoxin B. Taken together, our findings indicate that IFN-gamma does not hinder but instead facilitates induction of long-term allograft survival possibly by limiting expansion of activated T cells.

Abatacept↗
PubMed1998

The role of IgG1 and IgG2 in trimellitic anhydride-induced allergic response in the guinea pig lung.

Trimellitic anhydride (TMA) is a small molecular weight chemical used in the paint and plastics industry that can cause asthma-like symptoms in humans. Guinea pigs sensitized intradermally with TMA will respond to antigen challenge with asthma-like symptoms, including an immediate bronchoconstriction and a delayed cellular infiltration into the lung, particularly eosinophil infiltration. Sensitized guinea pigs produce TMA-specific IgG1, which is thought to be important in asthmatic reactions in this animal model; however, they also produce TMA-specific IgG2 antibody. The purpose of the present study was to determine the role of IgG1 and IgG2 in the TMA-induced immediate bronchoconstriction and delayed cellular infiltration in the guinea pig. Guinea pigs were passively sensitized by intratracheal instillation of TMA-specific IgG2, an antibody preparation enriched with TMA-specific IgG1, or a combination of the two. The allergic response was induced by intratracheal instillation of TMA conjugated to guinea pig serum albumin (TMA-GPSA). A significantly greater bronchoconstrictor response was observed in animals sensitized with a combination of the IgG2 and IgG1 preparation compared to those sensitized with IgG2 or the IgG1 preparation alone. Cellular infiltration was quantified 24 h after antigen challenge by differential cell counts of bronchoalveolar lavage (BAL) cells as well as by using eosinophil peroxidase (EPO) and myeloperoxidase (MPO) activity as a measure of the numbers of eosinophils and neutrophils, respectively. In the BAL, passively sensitizing with IgG2 alone resulted in an increase in both TMA-induced MPO and EPO activity. In contrast, in the lung, passively sensitizing with a partially purified preparation of TMA-specific IgG1 alone resulted in a significant increase in TMA-induced EPO activity. Passively sensitizing with IgG2 in conjunction with the IgG1 preparation resulted in an enhanced cellular infiltration and lung injury over that seen with either antibody preparation alone. These data demonstrate an augmentation of IgG1-mediated responses by the addition of IgG2 and suggest a significant role for both subclasses of IgG antibodies in this guinea pig model of TMA-induced occupational asthma.

Aged↗