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Biomedical subjects

D T Umetsu

Publications and source records attributed to D T Umetsu.

At least 55 records · Page 3Linked to original sources
PubMed1996

Reconstitution of germinal center formation in nude mice with Th1 and Th2 clones.

We investigated the ability of hemocyanin (KLH)-specific cloned CD4+ T cells expressing defined cytokine profiles to support germinal center (GC) formation in syngeneic athymic recipients in response to hapten-KLH challenge. Th1 clones producing IL-2 and IFN-gamma did not by themselves increase GC production above background, while Th2 cells producing IL-4 and IL-5 did. However, the combination of Th1 and Th2 cytokines was more effective than Th2 cytokines alone, suggesting a synergistic effect in this aspect of their help for B cells. In contrast to GC formation, antibody production could be induced with Th1 or Th2 clones given separately (Th1 clones inducing IgG2a, and Th2 clones inducing IgG1 and IgE). These results indicate that the T cell requirements for GC production are different from those for isotype switching and Ig secretion. It is postulated that the synergy between Th1 and Th2 cells in the induction of GC formation reflects the synergy between Th1 and Th2 cytokines, such as IFN-gamma and IL-5, in promotion of GC cell proliferation.

Adoptive Transfer↗
PubMed1996

Cross-linking of the CD40 ligand on human CD4+ T lymphocytes generates a costimulatory signal that up-regulates IL-4 synthesis.

Although there is good evidence that the induction of IL-4 synthesis in CD4+ T lymphocytes is favored by Ag presentation by B cells and not macrophages, the precise molecular signals provided by B cells to T cells that enhance IL-4 synthesis are not clear. To examine this issue, we established an APC-independent system to activate highly purified T cells and induce cytokine synthesis, using immobilized mAbs against several T cell surface molecules, including CD3, CD28, and the CD40 ligand (CD40L). The counter-receptors for all three of these molecules are expressed on B cells, and include CD40, which is expressed primarily on B cells, but also on dendritic cells and thymic epithelium. We found that IL-4 synthesis was greatly enhanced by triggering of CD40L on the T cell surface in conjunction with ligation of CD3/TCR and CD28, whereas ligation of CD3/TCR and CD28 in the absence of CD40L triggering resulted in little or no IL-4 synthesis. CD40L costimulation greatly enhanced IL-4 synthesis both in T cells from normal nonallergic adult subjects as well as in naive T cells from cord blood. Furthermore, we demonstrated that IL-4 synthesis was optimally enhanced when the strength of the CD3/TCR signal was limiting, while IL-4 synthesis was inhibited when CD3/TCR stimulation was maximal. These studies confirm that IL-4 synthesis can be induced in normal T lymphocytes in the absence of exogenous IL-4, and demonstrate that CD40L costimulation is of fundamental importance in regulation of IL-4 production. In addition, these findings provide a mechanism by which B cells preferentially enhance IL-4 synthesis in T cells at low Ag concentrations.

Adult↗
PubMed1996

High copy number I-Ab transgenes induce production of IgE through an interluekin 4-dependent mechanism.

To better understand the role of class II major histocompatibility complex molecules in both normal and autoimmune responses, we have produced a series of I-Ab transgenic mice. One of these transgenic constructs, designated NOD.PD, has the sequence of the NOD beta chain (Abeta(g7)) except at positions 56 and 57, where Pro-Asp replaces His-Ser. Several NOD.PD transgenic lines have been produced. One line of these mice carried a very high number of copies (>50) of the NOD.PD transgene. As has been described in other mice carrying high copy numbers of I-Ab transgenes, B-cell development was abnormal. The steady state numbers of mature B cells (IgM+/IgD(hi)) in the periphery were greatly reduced in transgenic mice compared to nontransgenic littermates. Surprisingly, rather than being accompanied by a generalized hypogammaglobulinemia, this B-cell deficiency was accompanied by elevated concentrations of IgG1 and IgE in the serum. Conversely, the levels of IgG2a were reduced in transgenic mice compared to nontransgenic littermates. Because this isotype pattern was characteristic of interleukin (IL)-4-induced class-switching, we then investigated the role of IL-4 in causing the observed phenotype. We crossed the high copy number transgenic mice with an IL-4-deficient strain of mice. As expected, the elevated levels of IgE in high copy number transgenic mice were eliminated when the IL-4 gene was inactivated. However, the reduction in the number of B cells was not ameliorated. These data indicate that the primary defect caused by the transgene was to reduce the number of B cells in these mice. This reduction was accompanied by a secondary increase in IL-4 production, which drove the remaining B cells toward the production of IgGl and IgE.

Animals↗
PubMed1996

Ligation of TAPA-1 (CD81) or major histocompatibility complex class II in co-cultures of human B and T lymphocytes enhances interleukin-4 synthesis by antigen-specific CD4+ T cells.

We have previously shown that CD4+ T cells from allergic individuals are predisposed to producing interleukin (IL)-4 in response to allergens. IL-4 production could be modulated by antigen concentration as well as by the type of antigen-presenting cells (APC), with B lymphocytes inducing greater quantities of IL-4 than monocytes. Using this system we examined IL-4 synthesis after culture of CD4+ T cells with B cells, monocytes, or both, as APC in the presence of allergen and a monoclonal antibody against CD81 (TAPA-1), a member of the TM4 superfamily of proteins that regulates activation, proliferation and trafficking of B cells. Addition of anti-CD81 mAb during culture enhanced IL-4 synthesis by 2- to 70-fold over that using an isotype-matched control mAb. Furthermore, anti-CD81 mAb enhanced IL-4 synthesis in CD4+ T cells only when CD4+ T cells were cultured with B cells but not monocytes as APC, indicating that anti-CD81 mAb affected IL-4 synthesis in T cells via interactions with B cells. However, pretreatment of either population separately with anti-CD81 mAb prior to culture had no effect on subsequent IL-4 synthesis, suggesting a requirement for temporal or cooperative interactions between T and B lymphocytes. In addition, anti-CD81 mAb enhanced IL-4 production but reduced CD4+ T cell antigen-specific proliferation, demonstrating that IL-4 production and proliferation by CD4+ T cells were inversely related. Finally, mAb to major histocompatibility complex class II but not to anti-CD19 also enhanced IL-4 synthesis when B lymphocytes were used as APC. In all instances, enhancement of CD4+ IL-4 synthesis correlated with the presence of large cell aggregates in T-B lymphocyte cocultures. These results indicate that the capacity of B cells to induce IL-4 can be significantly enhanced by ligation of particular molecules on their surface and should aid in the design of treatments for diseases in which modulation of the cytokine profile would be beneficial.

Antibodies, Monoclonal↗
PubMed1996

Regulation of disease susceptibility: decreased prevalence of IgE-mediated allergic disease in patients with multiple sclerosis.

The development of restricted cytokine profiles by subsets of CD4+ T cells is a pivotal point in the regulation of immune responses. T cells producing Th1 cytokines (IL-2 and interferon-gamma) induce cell-mediated immunity, whereas T cells producing Th2 cytokines (IL-4, IL-5, and IL-10) play a prominent role in the induction of humoral immunity. We examined a group of patients with multiple sclerosis, a disease caused by excess production of Th1 cytokines in myelin-reactive T cells, and control patients with noninflammatory neuroconvulsive disorders, for the presence of allergic disease, which is caused by excess production of Th2 cytokines in allergen-specific T cells. The patients with multiple sclerosis had significantly fewer allergic symptoms, a lower number of positive allergen-specific IgE test results, and lower composite allergy indexes than control subjects. These results demonstrate that the prevalence of IgE-mediated allergic disease is decreased in a group of patients with multiple sclerosis and support the hypothesis that genetic factors that promote susceptibility to Th1-mediated inflammatory disease in human beings protect against the development of Th2-mediated disease.

Adult↗
PubMed1996

Differential production of IL-12 in BALB/c and DBA/2 mice controls IL-4 versus IFN-gamma synthesis in primed CD4 lymphocytes.

The profile of cytokines produced by CD4 T cells is profoundly influenced by the presence of IL-12. Here we demonstrate that during re-stimulation of antigen-specific immune responses in vitro, antigen-primed lymph node cells from DBA/2 mice produced 3- to 30-fold more IL-12 than did cells from BALB/c mice, which are identical at the major histocompatibility locus. The strain differences in IL-12 production were observed only in antigen-driven responses (and not in responses induced by bacterial products), and were dependent upon an interaction between CD4 T cells and lymph node adherent cells. In addition, differences in the quantity of IL-12 produced by DBA/2 and BALB/c antigen-presenting cells (APC) was not dependent on differential production of IFN-gamma by T cells, since APC from DBA/2 mice still produced much greater quantities of IL-12 than did BALB/c APC when each was cultured with the same H-2d-restricted Th2 clones, in the complete absence of IFN-gamma, or when each was cultured with primed (BALB/c x DBA/2)F1 T cells. The level of IL-12 produced in the cultures critically affected cytokine production in CD4 T cells, since neutralization of endogenous IL-12 in DBA/2 cultures, which are predisposed towards developing Th1 responses, reduced IFN-gamma production and enhanced IL-4 synthesis to levels normally seen in BALB/c cultures, which are predisposed toward developing Th2 responses. We propose therefore that differential production of antigen-driven IL-12 is a mechanism by which the genetic background in DBA/2 and BALB/c mice can affect the pattern of cytokine synthesis by T cells during the development of adaptive immune responses.

Adjuvants, Immunologic↗
PubMed1995

Severe combined immunodeficiency with absence of peripheral blood CD8+ T cells due to ZAP-70 deficiency.

During ontogeny, T lymphocytes are selected for CD4 or CD8 expression in part by their ability to signal properly through the TCR. Transmission of such signals requires the activation of specific cytoplasmic protein tyrosine kinases (PTKs) which lead to T-cell activation through poorly understood mechanisms. Recently, mutations in one such PTK, called ZAP-70, have been shown to be responsible for a rare, autosomal recessive form of severe combined immunodeficiency (SCID) in humans. This distinctive SCID syndrome is characterized by the selective absence of peripheral CD8+ T cells and by abundant circulating CD4+ T cells that fail to respond to TCR-mediated stimuli in vitro. In this report, we describe in detail the clinical and laboratory findings in one patient with ZAP-70 deficiency and discuss the insights provided by this disorder into the pathways of TCR signal transduction and T-cell development.

B-Lymphocytes↗
PubMed1995

IL-12 inhibits the production of IL-4 and IL-10 in allergen-specific human CD4+ T lymphocytes.

IL-12 influences cytokine synthesis in unprimed CD4+ T cells by enhancing IFN-gamma synthesis and enhancing the development of Th1 cells, but its effects upon Ag-primed T cells, which are thought to have relatively fixed cytokine profiles, is less clear. We investigated the capacity of IL-12 to modify cytokine synthesis in allergen-specific human CD4+ T lymphocytes from allergic donors after in vitro stimulation. CD4+ T cells were obtained from the peripheral blood of subjects with allergic rhinitis, depleted of activated T cells, and cultured with APCs and allergen. IL-12 dramatically inhibited the development of IL-4 and IL-10 synthesis, while it enhanced T cell secretion of IFN-gamma and IL-2, and enhanced Ag-specific T cell proliferation. The inhibitory effect of IL-12 on IL-4 synthesis was not dependent on the presence of IFN-gamma, was greatest when IL-12 was added at the initiation of culture, and was minimal when added late, indicating that resting memory CD4+ T cells were more sensitive than activated CD4+ T cells to the effects of IL-12. The effect of IL-12 on IL-4 and IL-10 synthesis was not dependent on the APC type, because IL-12 decreased IL-4 synthesis when either B cells or monocytes served as APCs. These results indicate that IL-12 may be therapeutically beneficial in the treatment of allergic diseases in which allergen-specific T cells characteristically produce enhanced quantities of IL-4 and IL-10.

Antigen-Presenting Cells↗
PubMed1995

IL-12 inhibits IL-4 synthesis in keyhole limpet hemocyanin-primed CD4+ T cells through an effect on antigen-presenting cells.

Although IL-12 is known to enhance IFN-gamma synthesis in unprimed CD4+ T cells, the effect of IL-12 on IL-4 synthesis in primed CD4+ T cells, which are thought to have relatively fixed cytokine profiles, has not been clearly examined. We examined the effects of IL-12 on cytokine production by CD4+ keyhole limpet hemocyanin (KLH)-primed memory lymph node T cells and by already established KLH-specific CD4+ T cell clones. First, we found that the presence of IL-12 greatly reduced the development of IL-4 synthesis in resting but not activated memory CD4+ T cells. Although IL-12 did not inhibit the production of IL-4 in cloned Th2 effector cells, it greatly inhibited the development of IL-4 synthesis in primed CD4+ T cells taken from the lymph nodes of mice previously immunized with KLH. Secondly, we found that IL-12 inhibited IL-4 synthesis either when directly added to cultures of T cells or when APC were preincubated in IL-12. Inasmuch as the enhancing effect of IL-12 on IFN-gamma synthesis occurred optimally only when the T cells were cultured directly in IL-12, these studies indicate that IL-12 affects IL-4 synthesis via a mechanism that involves APC, a process that differs from that by which it affects IFN-gamma synthesis. These studies also indicate that the administration of IL-12 would be clinically useful in treating patients, for example those with allergic disease or lepromatous leprosy, in whom memory T cells inappropriately overproduce IL-4.

Animals↗
PubMed1995

Interleukin 4 production by CD4+ T cells from allergic individuals is modulated by antigen concentration and antigen-presenting cell type.

We have previously shown that CD4+ T cells from allergic individuals are predisposed to produce interleukin (IL)-4 in response to allergens, and that allergen immunotherapy greatly reduced IL-4 production in an allergen-specific fashion. The mechanism that results in the reduction of IL-4 synthesis in treated individuals is unknown, but because clinical improvement during immunotherapy is associated with the administration of the highest doses of allergen, we hypothesized that high concentration of allergen results in the downregulation of IL-4 synthesis in CD4+ T cells. In this report, we demonstrated that CD4+ T cells from allergic donors produced high levels of IL-4 when stimulated with low concentrations of allergen (0.003-0.01 micrograms/ml), particularly when B cell-enriched populations presented the antigen. In contrast, the same responding CD4+ T cell population produced little IL-4 when stimulated with high concentrations of allergen (10-30 micrograms/ml), especially when monocytes were used as antigen-presenting cells (APC). The quantity of IL-4 produced was also found to be inversely related to the extent of proliferation of the CD4+ T cells in response to allergen/antigen; maximal proliferation of CD4+ T cells occurred in response to high concentrations of antigen when IL-4 production was minimal. Antigen presentation by B cell-enriched populations, instead of monocytes, induced less CD4+ T cell proliferation, but induced much greater IL-4 synthesis. Moreover, the addition of increasing numbers of APC (either B cells or monocytes) to cultures containing a constant number of responder T cells resulted in increased T cell proliferation and decreased IL-4 production. These results indicate that the circumstances under which memory T cells are activated, as well as the strength of the proliferative signal to T cells, greatly affect the quantity of IL-4 produced. Thus, our observations that the cytokine profile of allergen-specific memory CD4+ T cells can indeed be modulated by the antigen dose and APC type suggest that methods that preferentially enhance allergen uptake by monocytes and that enhance T cell proliferation will improve the clinical efficacy of immunotherapy in the treatment of allergic disease.

Allergens↗
PubMed1995

Regulation of the interaction between Th1 and Th2 T cell clones to provide help for antibody production in vivo.

On the premise that an individual with an intact immune system has the capability to develop both cellular and antibody immune responses supported by the balance between the lymphokines secreted by T helper (Th) cells, we studied the interaction between different types of Th cell clones in vivo and the parameters that may affect this interaction. We used an adoptive transfer system in which nude or lethally irradiated mice were reconstituted with histocompatible CD4+ keyhole limpet hemocyanin (KLH)-specific T cell clones with defined lymphokine profiles. This approach allowed us to study the effects of the cognate interaction between T and B cells in the presence of a defined set of lymphokines. We demonstrated that the co-transfer of both subsets of Th cells resulted in increased production of IgA, and decreased production of IgE and IgG2a. The concomitant presence of both cell types also increases their functional survival in vivo. We have shown that in the presence of a Th2 clone, higher immunization doses (above 100 micrograms trinitrophenol (TNP)-KLH/mouse) result in increased production of IgE and IgG1. In contrast, when a Th1 clone is present, low immunization doses (less than 50 micrograms TNP-KLH/mouse) resulted in increased production of IgG2a. We were also able to show that the neutralization of interleukin-4(IL-4) and or interferon-gamma (IFN-gamma) was sufficient to abrogate most of the regulatory effects caused by the Th2 or the Th1 clone respectively. Our results indicate that the subset of T cell(s) transferred determines the type of response obtained. In addition, the data presented indicate that the antigen dose used for immunization can modulate the quantitative parameters of the response. Furthermore, we have shown that the interaction between the two subsets of T cells in vivo is characterized by both antagonistic and agonistic effects and that most of the regulatory effects exerted by one subset over the other are mediated by IL-4 or IFN-gamma.

Animals↗
PubMed1995

IL-4 synthesis by in vivo-primed memory CD4+ T cells: II. Presence of IL-4 is not required for IL-4 synthesis in primed CD4+ T cells.

Previous studies have shown that the presence of IL-4 is required for the development of IL-4 synthesis in naive CD4+ T cells. The purpose of our current studies was to investigate the role of IL-4 in the development of IL-4 synthesis in primed memory T cells. We therefore examined CD4+ T cells taken from lymph nodes of BALB/c mice immunized with keyhole limpet hemocyanin (KLH) and restimulated in vitro with KLH. Our results with such primed resting CD4+ T cells programmed to produce IL-4 indicated that the production of IL-4 did not require the presence of IL-4 (although the presence of IL-2 was absolutely necessary), and was only slightly limited by the presence of anti-IL-4 MAb. These results with resting memory T cells were not biased by the presence of activated T cells already producing substantial quantities of IL-4, since we demonstrated that high-density memory T cells could produce IL-4 in the absence of IL-4, and because T cells that actively produce IL-4 do not persist in vivo very long after antigen exposure. These results indicate that IL-4 synthesis in T cells committed to IL-4 production can indeed occur in the absence of IL-4 when culture conditions have been optimized and suggest that therapies with anti-IL-4 MAb or with soluble IL-4 receptors designed to control the development of IL-4 synthesis in memory T cells from individuals exhibiting excessive IL-4 synthesis will be unsuccessful. Therefore, other therapies, for example, utilizing IL-12, will be required to modulate the relatively fixed programs in memory T cells that direct the development of cytokine synthesis.

Adjuvants, Immunologic↗
PubMed1995

IL-4-based helper activity of CD4+ T cells is radiation sensitive.

The capacity of CD4+ T cells to induce IgG synthesis in B cells has been known to be radioresistant for more than 20 years. However, the radiation sensitivity of helper T cells with regard to their ability to induce the synthesis of isotypes other than IgG has not been studied. We therefore irradiated KLH-primed lymph node T cells and examined their capacity to induce IgG, IgM, and IgE synthesis in hapten-primed B cells. We demonstrated that while the capacity of KLH-primed lymph node cells to induce IgG synthesis was not affected by irradiation, the capacity of such T cells to induce IgE synthesis was greatly reduced by gamma-irradiation. This was consistent with our observations that IL-4 and IL-5 synthesis in such cells was greatly diminished by irradiation, whereas IL-2 synthesis was only minimally affected. A similar differential sensitivity to irradiation of the helper activity of Th1 and Th2 clones was observed with regard to their ability to induce IgE and IgG synthesis under cognate conditions. Irradiation greatly inhibited the capacity of Th2 clones to induce IgE synthesis, but only minimally affected the capacity of Th1 clones to induce IgG synthesis in primed B cells. The capacity of irradiated Th2 clones to induce IgE synthesis was restored by the addition of IL-4 and IL-5. These results taken together indicated that the sensitivity to irradiation of T helper cells with regard to the induction of IgE but not IgG synthesis was due to the sensitivity to irradiation of the production of IL-4 but not of IL-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Human alveolar macrophages present antigen ineffectively due to defective expression of B7 costimulatory cell surface molecules.

Alveolar macrophages, resident phagocytic cells in the lung that derive from peripheral blood monocytes, are paradoxically ineffective in presenting antigen to T cells. We found that antigen presentation by alveolar macrophages could be restored by the addition of anti-CD28 mAb to cultures of T cells and macrophages, indicating that costimulation by alveolar macrophages via the CD28 pathway was defective. In addition, we found that alveolar macrophages activated with IFN-gamma failed to express B7-1 or B7-2 antigens, which normally ligate CD28 on T cells and provide a costimulatory signal required for the activation of T cells. These observations are the first to demonstrate the inability of a "professional" antigen-presenting cell type to effectively express the costimulatory molecules B7-1 and B7-2. Inasmuch as immune reactions within the lung are inevitably associated with inflammatory injury to pulmonary tissue, these observations suggest that reduced expression of B7-1 and B7-2 by alveolar macrophages may be advantageous, as a critical mechanism involved in the induction of peripheral tolerance to the abundance of antigens to which mucosal tissues are continuously exposed.

Adult↗
PubMed1994

Heterogeneity of phenotype in two siblings with adenosine deaminase deficiency.

Adenosine deaminase (ADA) deficiency is the cause of about one third of the autosomal recessively inherited cases of severe combined immunodeficiency. Disease severity in ADA deficiency is variable, presumably related in part to heterogeneity in the genotypes causing the disease. We now report on two children in a single family with ADA deficiency who presented with distinct clinical courses. One child presented with severe immunodeficiency and recurrent infections that led to the diagnosis of severe combined immunodeficiency and ADA deficiency at 7 months of age. The older child, who was diagnosed at 3 years of age (after the diagnosis of the younger child), did not have a history of serious or opportunistic infections. Although she was lymphopenic, immune responsiveness was intact, in terms of antibody production, delayed-type hypersensitivity, and in vitro T-cell function. The difference in clinical course in these two siblings is an important observation and demonstrates that the phenotypic expression of ADA deficiency can vary within a family, even in a situation in which protective isolation from infectious pathogens was not a factor in causing the milder course. These observations indicate that expression of disease severity in ADA deficiency may depend to a significant degree on environmental factors and/or on heterogeneity at other genetic loci, which may regulate or modify the expression of the ADA gene or the activity of its product. Furthermore, these observations highlight the importance of recognizing patients with ADA deficiency who present with less severe disease and support the impression that functional immunity in patients with the "late-onset" form of ADA deficiency can deteriorate over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1994

Correct splicing despite mutation of the invariant first nucleotide of a 5' splice site: a possible basis for disparate clinical phenotypes in siblings with adenosine deaminase deficiency.

Adenosine deaminase (ADA) deficiency usually causes severe combined immune deficiency in infancy. Milder phenotypes, with delayed or late onset and gradual decline in immune function, also occur and are associated with less severely impaired deoxyadenosine (dAdo) catabolism. We have characterized the mutations responsible for ADA deficiency in siblings with striking disparity in clinical phenotype. Erythrocyte dAdo nucleotide pool size, which reflects total residual ADA activity, was lower in the older, more mildly affected sib (RG) than in her younger, more severely affected sister (EG). Cultured T cells, fibroblasts, and B lymphoblasts of RG had detectable residual ADA activity, while cells of EG did not. ADA mRNA was undetectable by northern analysis in these cells of both patients. Both sibs were found to be compound heterozygotes for the following novel splicing defects: (1) a G+1-->A substitution at the 5' splice site of IVS 2 and (2) a complex 17-bp rearrangement of the 3' splice site of IVS 8, which inserted a run of seven purines into the polypyrimidine tract and altered the reading frame of exon 9. PCR-amplified ADA cDNA clones with premature translation stop codons arising from aberrant pre-mRNA splicing were identified, which were consistent with these mutations. However, some cDNA clones from T cells of both patients and from fibroblasts and Epstein-Barr virus (EBV)-transformed B cells of RG, were normally spliced at both the exon 2/3 and exon 8/9 junctions. A normal coding sequence was documented for clones from both sibs. The normal cDNA clones did not appear to arise from either contamination or PCR artifact, and mosaicism seems unlikely to have been involved. These findings suggest (1) that a low level of normal pre-mRNA splicing may occur despite mutation of the invariant first nucleotide of the 5' splice donor sequence and (2) that differences in efficiency of such splicing may account for the difference in residual ADA activity, immune dysfunction, and clinical severity in these siblings.

Adenosine Deaminase↗