Biomedical subjects

Thomas J Waldschmidt

Publications and source records attributed to Thomas J Waldschmidt.

14 recordsLinked to original sources

PubMed2006

Characterization of (4-hydroxy-3-nitrophenyl)acetyl (NP)-specific germinal center B cells and antigen-binding B220- cells after primary NP challenge in mice.

Previous studies examining the primary germinal center (GC) response to SRBC in mice demonstrated a steady ratio of IgM(+) to isotype-switched GC B cells and a persistent population of GC B cells with a founder phenotype. These characteristics held true at the inductive, plateau, and dissociative phases of the GC response, suggesting a steady-state environment. To test whether these characteristics apply to the primary response of other T cell-dependent Ags, the present study examined the GC response after challenge with (4-hydroxy-3-nitrophenyl)acetyl (NP) in C57BL/6 mice. Multiparameter flow cytometric analysis was used to assess the phenotype of splenic NP-reactive cells at multiple time points after immunization. Results of these studies demonstrated the characteristics of the SRBC-induced GC reaction to be fully maintained in the NP response. In particular, there was a steady ratio of nonswitched to switched B cells, with the majority of NP-reactive GC B cells displaying IgM. In addition, a substantial frequency of B220(-) NP-binding cells was observed in the spleen at later time points after NP challenge. Although these cells were IgE(+), they were found to express both kappa and lambda L chains and display the high-affinity IgE Fc (FcepsilonRI) receptor, suggesting that this population is not of B cell origin. Adoptive transfer studies further demonstrated the B220(-) NP-binding subset to be derived from the myeloid lineage.

Animals↗

PubMed2006

Alcohol and inflammation and immune responses: summary of the 2005 Alcohol and Immunology Research Interest Group (AIRIG) meeting.

The 10th annual meeting of the Alcohol and Immunology Research Interest Group (AIRIG) was held at Loyola University Medical Center, Maywood, Illinois on November 18, 2005. The AIRIG meeting was held to exchange new findings and ideas regarding the profound suppressive effects of alcohol exposure on the immune system. The event consisted of five sessions, two of which featured plenary talks from invited speakers, two with oral presentations from selected abstracts, and a final poster session. Participants presented a range of novel information focused on ethanol-induced effects on innate and adaptive immunity after either acute or chronic exposure. In particular, participants offered insights into the negative effects of ethanol on the innate processes of adhesion, migration, inflammation, wound repair, and bone remodeling. Presentations also focused on the means by which ethanol disrupts activation of macrophages and dendritic cells (DC), especially stimulation mediated by Toll-like receptor ligands. Additional talks provided new data on the means by which ethanol suppresses adaptive immunity, with an emphasis on DC-mediated activation of T cells, effector T cell activity, and T cell-driven B cell responses.

Animals↗

PubMed2005

Critical role for Stat3 in T-dependent terminal differentiation of IgG B cells.

Stat proteins are latent cytoplasmic transcription factors that are crucial in many aspects of mammalian development. In the immune system, Stat3 has distinct roles in T-cell, neutrophil, and macrophage function, but a role for Stat3 in B-cell development, particularly in the terminal differentiation of B cells into antibody-secreting plasma cells, has never been directly tested. In this study, we used the Cre/lox system to generate a mouse strain in which Stat3 was conditionally deleted in the B-cell lineage (Stat3(fl/fl)CD19(Cre/+)). B-cell development, establishment of the peripheral B-cell compartment, and baseline serum antibody levels were unperturbed in Stat3(fl/fl)CD19(Cre/+) mice. Strikingly, Stat3(fl/fl)CD19(Cre/+) mice displayed profound defects in T-dependent (TD) IgG responses, but normal TD IgM, IgE, and IgA responses and T-independent (TI) IgM and IgG3 responses. In addition, germinal center (GC) formation, isotype switching, and generation of memory B cells, including IgG+ memory cells, were all intact in Stat3(fl/fl)CD19(Cre/+) mice, indicating that the requirement for Stat3 was limited to plasma cell differentiation. These results demonstrate a profound yet highly selective role for Stat3 in TD IgG plasma cell differentiation, and therefore represent a unique example of a transcription factor regulating isotype-specific terminal B-cell differentiation.

Animals↗

PubMed2005

A missense mutation in pstpip2 is associated with the murine autoinflammatory disorder chronic multifocal osteomyelitis.

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory disorder that primarily affects bone but is often accompanied by inflammation of the skin and/or gastrointestinal tract. The etiology is unknown but evidence suggests a genetic component to disease susceptibility. Although most cases of CRMO are sporadic, there is an autosomal recessive syndromic form of the disease, called Majeed syndrome, which is due to homozygous mutations in LPIN2. In addition, there is a phenotypically similar mouse, called cmo (chronic multifocal osteomyelitis) in which the disease is inherited as an autosomal recessive disorder. The cmo locus has been mapped to murine chromosome 18. In this report, we describe phenotypic abnormalities in the cmo mouse that include bone, cartilage and skin inflammation. Utilizing a backcross breeding strategy, we refined the cmo locus to a 1.3 Mb region on murine chromosome 18. Within the refined region was the gene pstpip2, which shares significant sequence homology to the PSTPIP1. Mutations in PSTPIP1 have been shown to cause the autoinflammatory disorder PAPA syndrome (pyogenic arthritis, pyoderma gangrenosum and acne). Mutation analysis, utilizing direct sequencing, revealed a single base pair change c.293T --> C in the pstpip2 gene resulting in a highly conserved leucine at amino acid 98 being replaced by a proline (L98P). No other mutations were found in the coding sequence of the remaining genes in the refined interval, although a 50 kb gap remains unexplored. These data suggest that mutations in pstpip2 may be the genetic explanation for the autoinflammatory phenotype seen in the cmo mouse.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Cooperation between platelet-derived CD154 and CD4+ T cells for enhanced germinal center formation.

It has been demonstrated previously that platelet-derived CD154 communicates with the adaptive immune compartment, enhancing B and T cell responses in CD154(-/-) mice. The presence of platelets was also shown to be necessary for optimal production of immunoglobulin G (IgG) in normal C57BL/6 mice. These data led us to hypothesize that platelets perform a sentinel function, quickly relaying activating signals to the adaptive immune compartment. Here, we report that platelet-derived CD154 increases serum IgG levels and germinal center formation under conditions where antigen-specific CD4(+) T cell numbers are limiting. We propose that in the physiologic setting where antigen-specific B and T cells are rare, platelets function to enhance signals required for robust adaptive humoral immunity.

Animals↗

PubMed2005

The primary germinal center response in mice.

The germinal center (GC) is an important anatomical site for the development of high affinity antibodies during T-cell dependent B cell responses. Although the importance of the GC response to humoral immunity is well known, much remains to be elucidated about GC induction, maintenance and regulation. Recent studies examining the GC response in mice have identified key molecules expressed on follicular dendritic cells that support the differentiation of GC B cells, revealed essential chemokines that direct the organization of light and dark zones, and demonstrated potentially novel roles for TNF family members in the differentiation of GC B cells.

Animals↗

PubMed2004

Chronic ethanol ingestion by mice increases expression of CD80 and CD86 by activated macrophages.

Results from previous studies from our laboratory have shown that T cells obtained from the spleens of C57BL/6 mice that consumed ethanol chronically have increased expression of activation markers and increased second signal-independent production of interferon-gamma (IFN-gamma). We now report that in vitro-activated CD11b(+) splenocytes obtained from C57BL/6 and BALB/c mice that consumed ethanol chronically express increased levels of the T cell co-stimulatory molecules CD80 and CD86. CD11b(+) splenocytes encompass at least two populations: the CD11b(+)Gr.1(-) population, which is primarily monocytes-macrophages, and a smaller CD11b(+)Gr.1(+) population, which is in the myelocytic-monocytic cell series and contains precursors of both macrophages and neutrophils. Evaluation of cultures of purified CD11b(+) cells, obtained from mice that consumed ethanol chronically, incubated overnight, showed increased up-regulation of CD80 and CD86 expression on Gr.1(-) mouse splenic macrophages. Results of functional studies of purified CD11b(+) cells have demonstrated that CD11b(+) cells obtained from C57BL/6 mice that were exposed to ethanol chronically secrete higher levels, in comparison with the levels secreted by CD11b(+) cells obtained from control animals, of nitric oxide and several proinflammatory cytokines after stimulation by the oligodeoxynucleotide (ODN) CpG 1826. These findings indicate that CD11b(+) splenocytes are in some way sensitized to activating stimuli by chronic ethanol exposure in vivo. Such cells may contribute to systemic immunodysregulation, including T-cell activation, by providing abnormal second signals to T cells, or through excessive release of cytokines, such as interleukin (IL)-6 or IL-12.

Alcohol Drinking↗

PubMed2004

T-cell activation after chronic ethanol ingestion in mice.

Chronic excessive consumption of ethanol causes immunodeficiency in human beings and in mice. Immunologic changes have been described in both species, including T-cell and innate immune system cell activation, among others. The features of chronic ethanol-induced activation have similarities in the two species, including an increased effector subset in both CD4+ and CD8+ T cells. There are also features of activation observed in the splenic macrophages of mice consuming ethanol chronically, including increased up-regulation of CD80 and CD86. Because these molecules are involved in T-cell-antigen-presenting cell interactions in vivo, it is of interest to ask whether these and other pathways of interaction are important in the T-cell activation and cytokine skewing described in chronic ethanol abuse. Preliminary findings from comparisons of wild-type, CD40 ligand knock-out, and CD28 knock-out C57BL/6 mice strongly support the suggestion of a critical role for T-cell-antigen-presenting cell interactions in the immune alterations observed in chronic ethanol abuse.

Alcoholism↗

PubMed2004

Expression of the cytoplasmic tail of LMP1 in mice induces hyperactivation of B lymphocytes and disordered lymphoid architecture.

The oncogenic EBV protein LMP1 mimics a dysregulated CD40 receptor in vitro. To compare CD40 and LMP1-mediated events in vivo, transgenic mice were engineered to express mouse CD40 (mCD40tg) or a protein with extracellular mCD40 and cytoplasmic LMP1 (mCD40-LMP1tg). Transgenic and CD40(-/-) mice were bred so that only the transgenic CD40 molecule is expressed in B cells, macrophages, and dendritic cells. mCD40-LMP1tg mice had normal lymphocyte subsets, and immunization elicited an antibody response featuring normal isotype switching, affinity maturation, and germinal center (GC) formation. However, unimmunized mCD40-LMP1tg mice had expanded immature and germinal center B cells, produced autoantibodies, exhibited marked splenomegaly and lymphadenopathy, and elevated serum IL-6. Thus, signaling through the LMP1 cytoplasmic tail results in amplified and abnormal mimicry of CD40 functions in vivo, indicating possible ways in which LMP1 contributes to the pathogenesis of EBV-associated human disease.

Animals↗

PubMed2004

The germinal center response.

The germinal center reaction is the foundation of T-cell-dependent humoral responses. Antigen-specific B cells recruited into germinal centers undergo a complex cellular program that allows for extensive expansion, isotype switching, somatic hypermutation, and differentiation into antibody-forming cells and memory cells. Importantly, the germinal center environment filters the repertoire of differentiating B cells such that high affinity variants are preferentially selected while low affinity or self-reactive clones are eliminated by apoptosis. The present article reviews the many processes that govern germinal center B-cell differentiation, as well as the cellular and molecular elements necessary to initiate and sustain a germinal center response. The major histologic features of the germinal center are also discussed, as well as the current dominant models of the germinal center reaction in humans and mice. Finally, a new model of murine B-cell differentiation is described on the basis of a multiparameter flow cytometric kinetic analysis of germinal center B cells.

Animals↗

PubMed2003

Antibody-mediated protection against cytotoxic T-cell escape in coronavirus-induced demyelination.

C57BL/6 (B6) mice infected with mouse hepatitis virus (MHV) strain JHM develop a clinically evident, demyelinating encephalomyelitis. Infectious virus can be isolated from the spinal cords of these mice and is invariably mutated in the immunodominant CD8 T-cell epitope recognized in this strain. We showed previously that these persistently infected mice did not mount a measurable serum anti-MHV neutralizing antibody response. Here we show that cytotoxic T-lymphocyte (CTL) escape was not detected in MHV-infected BALB/b mice (H-2(b) haplotype), even though the same CD8 T-cell epitopes were recognized as in B6 mice. BALB/b mice had 25-fold more MHV-specific antibody-secreting cells in the central nervous system, the site of infection, than B6 mice, suggesting that local production of anti-MHV antibody contributed to this absence of CTL escape. Additionally, administration of anti-MHV neutralizing antibody to infected B6 mice suppressed the development of CTL escape mutants. These findings indicate a key role for the anti-MHV antibody response in suppressing virus replication, thereby minimizing the emergence and competitive advantage of CTL escape mutants.

Animals↗

PubMed2002

Mice deficient in complement receptors 1 and 2 lack a tissue injury-inducing subset of the natural antibody repertoire.

Intestinal ischemia-reperfusion (IR) injury is initiated when natural Abs recognize neoantigens that are revealed on ischemic cells. Cr2(-/-) mice, deficient in complement receptors (CR)1 and CR2, demonstrate defects in T-dependent B-2 B cell responses to foreign Ags and have also been suggested to manifest abnormalities of the B-1 subset of B lymphocytes. To determine whether these CRs might play a role in the generation of the natural Abs that initiate intestinal IR injury, we performed experiments in Cr2(-/-) and control Cr2(+/+) mice. We found that Cr2(-/-) mice did not demonstrate severe intestinal injury that was readily observed in control Cr2(+/+) mice following IR, despite having identical serum levels of IgM and IgG. Pretreatment of Cr2(-/-) mice before the ischemic phase with IgM and IgG purified from the serum of wild-type C57BL/6 mice reconstituted all key features of IR injury, demonstrating that the defect involves the failure to develop this subset of natural Abs. Pretreatment with IgM and IgG individually demonstrates that each contributes to unique features of IR injury. In sum, CR2/CR1 play an unanticipated but critical role in the development of a subset of the natural Ab repertoire that has particular importance in the pathogenesis of IR injury.

Animals↗

PubMed2002

Abnormal T cell-dependent B-cell responses in SCID mice receiving allogeneic bone marrow in utero. Severe combined immune deficiency.

In allogeneic hematopoietic stem cell transplant recipients, restoration of humoral immunity is delayed and can remain impaired for years. In many severe combined immune deficiency (SCID) patients given haploidentical bone marrow (BM), lesions in humoral immunity are exacerbated by poor engraftment of donor B cells. The nature of these defects is important to understand as they render patients susceptible to infection. Previous work in mice suggested that in utero transplantation (IUT) of allogeneic BM might offer several advantages for the correction of primary immune deficiencies. In SCID mice given fully allogeneic BM in utero, the lymphoid compartment was restored with minimal evidence of graft-versus-host disease (GVHD). The present report examines B-cell reconstitution and function in mice that have received allogeneic IUT. Results are compared with those of adult mice given total body irradiation (TBI) followed by transplantation with allogeneic BM. In addition to enumerating the various B-cell subsets present in BM, spleen, and peritoneal cavity (PC), B-cell competence was assessed by challenging mice with T cell-independent (TI) and T cell-dependent (TD) antigens. The results demonstrated that all B-cell subsets in the BM and periphery were restored in allogeneic IUT and TBI mice, as were antibody responses after TI challenge. Upon immunization with TD antigens, however, IUT and TBI mice exhibited suboptimal responses as measured by the capacity to isotype switch and generate germinal center (GC) B cells. Thus, although allogeneic BM transplantation results in complete recovery of the B-cell compartment, certain elements of the humoral response remain defective.

Animals↗

PubMed2002

Chronic ethanol consumption by mice results in activated splenic T cells.

Previous studies have shown that T cells from human alcoholics overexpress activation or memory markers such as human leukocyte antigen-DR, CD45RO, CD57, and CD11b and may have reduced levels of CD62L. In those studies, we demonstrated that the increased CD57(+) T cell population rapidly produces interferon-gamma (IFN-gamma) and tumor necrosis factor alpha, independent of a second signal requirement, consistent with an increased effector T cell population. In contrast to the length of alcohol abuse by human alcoholics, most work with mice has involved 2-week ethanol exposures or less, which result in decreased IFN-gamma responses. In the present work, we have evaluated C57Bl/6 or BALB/c mice, which were administered 20% w/v ethanol in water for 3-13 weeks. In these mice, rapid cytoplasmic IFN-gamma expression by T cells after stimulation through the T cell receptor was significantly increased versus normals. Studies of surface-activation markers showed that T cells from chronically ethanol-fed mice had reduced CD62L expression and an increased percentage of CD44(hi) T cells. The CD44(hi) subset was largely second signal-independent for secreted IFN-gamma and interleukin (IL)-4 production at early times after stimulation. The enriched T cells of chronic ethanol mice secreted more IFN-gamma and IL-4 than controls and equivalent IL-2 at early times after stimulation (6-24 h). The overall results support the concept that in humans and mice, chronic alcohol exposure of sufficient duration results in T cell activation or sensitization in vivo and an increased percentage of the effector/memory subset.

Alcoholism↗