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Results for “Interleukin-4”

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At least 19 recordsLinked to original sources

PubMed2024

Accelerating diabetic wound healing by ROS-scavenging lipid nanoparticle-mRNA formulation.

Current treatment options for diabetic wounds face challenges due to low efficacy, as well as potential side effects and the necessity for repetitive treatments. To address these issues, we report a formulation utilizing trisulfide-derived lipid nanoparticle (TS LNP)-mRNA therapy to accelerate diabetic wound healing by repairing and reprogramming the microenvironment of the wounds. A library of reactive oxygen species (ROS)-responsive TS LNPs was designed and developed to encapsulate interleukin-4 (IL4) mRNA. TS2-IL4 LNP-mRNA effectively scavenges excess ROS at the wound site and induces the expression of IL4 in macrophages, promoting the polarization from the proinflammatory M1 to the anti-inflammatory M2 phenotype at the wound site. In a diabetic wound model of db/db mice, treatment with this formulation significantly accelerates wound healing by enhancing the formation of an intact epidermis, angiogenesis, and myofibroblasts. Overall, this TS LNP-mRNA platform not only provides a safe, effective, and convenient therapeutic strategy for diabetic wound healing but also holds great potential for clinical translation in both acute and chronic wound care.

Wound Healing↗

PubMed2026

Regulation of immune signal integration and memory by inflammation-induced chromosome conformation.

Three-dimensional (3D) genome conformation is central to gene expression regulation, yet our understanding of its contribution to rapid transcriptional responses, signal integration, and memory in immune cells is limited. Here, we study the molecular regulation of the inflammatory response in primary macrophages using integrated transcriptomic, epigenomic, and chromosome conformation data, including base pair-resolution Micro Capture-C. We demonstrate that interleukin-4 (IL-4) primes the inflammatory response in macrophages by stably rewiring 3D genome conformation, juxtaposing endotoxin-, interferon-gamma-, and dexamethasone-responsive enhancers to their cognate gene promoters. CRISPR-based perturbations of enhancer-promoter contacts or CCCTC-binding factor (CTCF) boundary elements show that IL-4-driven conformation changes are required for enhanced and synergistic endotoxin-induced transcriptional responses, as well as transcriptional memory following stimulus removal. Moreover, transcriptional memory mediated by changes in chromosome conformation can occur in the absence of changes in chromatin accessibility or histone modifications. Collectively, these findings demonstrate that rapid and memory transcriptional responses to immunological stimuli are encoded in the 3D genome.

Animals↗

PubMed1992

Responsiveness of chronic lymphocytic leukemia B cells activated via surface Igs or CD40 to B-cell tropic factors.

Recent studies performed in the laboratory have established that interleukin-4 (IL-4) used in combination with anti-CD40 monoclonal antibody (MoAb) 89 presented on Ltk- mouse fibroblasts stably expressing human Fc gamma RII/CDw32 (referred to as the CD40 system) sustains long-term proliferation of normal human B cells. In the present study, B-cell chronic lymphocytic leukemias (B-CLLs) activated through slgs or CD40 were examined for their capacity to proliferate and differentiate in response to various cytokines. Our results indicate that the outcome of IL-4 stimulation on the in vitro growth of B-CLL depends on the signalling pathway used for their activation. Whereas IL-4 did not display any growth-stimulatory effect on B-CLL activated by Ig cross-linking agents, it could stimulate DNA synthesis and enhance the viable cell recovery when leukemic B cells were cultured in the CD40 system. Most B-CLL samples were induced for IgM synthesis upon Staphylococcus aureus strain Cowan I stimulation. This Ig response was potentiated by IL-2 and antagonized by IL-4. Anti-CD40 MoAb used alone or in combination with cytokines (IL-1 alpha to IL-6, interferon gamma, tumor necrosis factor gamma, and transforming growth factor beta) failed to induce Ig secretion from B-CLL cells. No evidence for Ig isotype switching was obtained with the cytokines listed above, regardless of the mode of activation. Taken together, our results suggest that B-CLL cells can be partially released from their apparent maturation block by IL-2 and Ig cross-linking agents. In contrast, combinations of IL-4 and cross-linked anti-CD40 antibodies induced entry of B-CLL cell into cycle, but poorly stimulated their differentiation into Ig secreting cells.

Adult↗

PubMed2026

Increased IL4I1 expression predicts poor survival and modulates the immune microenvironment in acute myeloid leukemia.

BACKGROUND: The immunometabolic enzyme Interleukin-4-induced-1 (IL4I1) is implicated in cancer pathogenesis, yet its specific function and clinical relevance in acute myeloid leukemia (AML) remain unclear. METHODS: Comparative analysis of IL4I1 mRNA levels between AML patients and normal controls was performed using the Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. The Kaplan–Meier survival analysis was conducted to evaluate the prognostic value of IL4I1. Functional insights were derived from analyses of differentially expressed genes (DEGs), Gene Set Enrichment Analysis (GSEA), and Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. Immune infiltration was evaluated using the ssGSEA, ESTIMATE, quanTIseq and single-cell RNA sequencing (scRNA-seq) analysis. Finally, in vitro and in vivo functional experiments were perfromed to explore the impact of IL4I1 on AML progression and immunoregulation. RESULTS: IL4I1 expression was significantly elevated in AML compared to normal controls (p = 0.0004) and associated with poorer overall survival (p = 0.003). Bioinformatic analysis revealed that IL4I1 was linked to immune-related pathways—including humoral immune response, leukocyte interactions, and chemokine signaling—and to cellular amino acid metabolism. Its expression correlated with immune cell infiltration and checkpoint molecule expression. Experimentally, IL4I1 promoted leukemia cell proliferation in vitro and in vivo (p < 0.05). Furthermore, silencing IL4I1 suppressed M2 macrophage polarization and reduced secretion of inflammatory factors (p < 0.05). CONCLUSIONS: IL4I1 may serve as a potential biomarker for poor prognosis and an attractive target for immune-based therapeutic interventions in AML.

Humans↗

PubMed1992

Transgenes encoding mutant simian virus 40 large T antigens unmask phenotypic and functional constraints in thymic epithelial cells.

Transgenes encoding simian virus 40 (SV40) T antigen (Tag) can cause hyperplastic or tumorigenic lesions of desired but also of unforeseen cellular origin. Unexpectedly the human growth hormone-releasing factor (GRF) gene promoter directs expression of SV40 Tag specifically in thymic epithelial (TE) cells. Expression starts in the neonate, in which GRF-Tag+ cells display strict numerical and spatial constraints. Tag supersedes mechanisms that constrain these features and GRF-Tag mice develop thymic hyperplasia. To characterize GRF-Tag+ TE cells and their putative normal counterparts we compared phenotypic and functional effects caused by transgenes encoding mutant large T antigens. This strategy is applicable to any situation in which T antigen is used to alter development. One large Tag mutant (K1 + 5080) does not cause thymic hyperplasia. GRF-Tag (K1 + 5080)+ TE cells display strict temporal and spatial constraints throughout life. TE cells expressing other mutant large T antigens that cause thymic hyperplasia do not obey these rules and reveal that phenotypically distinct GRF-Tag+ TE-cell stages exist in vivo. Analysis of conditional immortal GRF-Tag(tsA58)+ TE cells expressing a temperature-sensitive large Tag shows that large Tag blocks differentiation in these cells. Phenotype and functions in these cells are regulated by cellular differentiation and interleukin 4 (IL-4).

Animals↗

PubMed2025

Modulation of Mettl5 alleviates airway allergy by regulating the epigenetic profile of M2 macrophages.

M2 macrophages (M2 cells) are known to be involved in both Th2 responses and immune regulation. However, the underlying mechanisms remain unclear. Functional abnormalities in macrophages are associated with airway allergy (AA). The objective of this study was to investigate the role of methyltransferase-like 5 (Mettl5) in macrophages and its potential to alleviate AA. In this study, an airway allergy (AA) mouse model was established using dust mite extracts (DME) as the specific antigen. M2 cells were collected from mice with and without AA. The role of Mettl5 in modulating the immune activities of M2 cells was assessed using both epigenetic and immunological approaches. We found that Mettl5 levels were elevated in airway M2 cells from mice with AA. The presence of Mettl5 in airway M2 cells was positively correlated with airway Th2 polarization in these mice. Airway M2 cells from AA mice exhibited impaired immune-suppressive function, which was resolved by ablating the Mettl5 gene in macrophages. Mettl5 was responsible for the hypermethylation of the Il10 promoter in airway M2 cells of AA mice. Exposure to DME induced Mettl5, which in turn recruited USP21 to deubiquitinate GATA3, thereby boosting IL-4 expression in M2 cells. Inhibiting Mettl5 restored the immune-suppressive capacity of airway M2 cells and mitigated experimental AA. In conclusion, Mettl5 plays a critical role in subverting the immune-regulatory capacity and enhancing IL-4 expression in M2 cells. Inhibition of Mettl5 can mitigate experimental AA by restoring the immune-regulatory functions of M2 cells.

Animals↗

PubMed1992

Application of BrdU/Hoechst-ethidium bromide two parameter flow cytometry in studying synchronous and non-synchronous mouse cells.

BrdU/Hoechst-EB bivariate flow cytometry has a wide application in the study of factors controlling cell cycle for asynchronous cells such as embryonic stem cells (ES), and for synchronous cells such as stimulated resting B cells (Bo). The technique allows one to calculate the average cell cycle duration time. ES cells are found to cycle every 8-10 h, and most B cells are 11-12 h, but there is a small subset of B cells with a cycle time of only 6-7 h. Using this technique, we also study the roles of different T lymphocytes on B cell activation when B cells are stimulated with anti-IgM antibodies (commonly used, anti-mu). Exposure to anti-mu recruits small B cells into the cell cycle, but arrests them in the G1 phase of the second cycle. Interleukin (IL) 4 is a costimulator of anti-mu. In addition, IL-4 is an S-phase progression factor. Contrary to that seen when B cells are stimulated by other mitogens, very few cells are in the G2 compartments after anti-mu plus IL-4 stimulation. This phenomenon is reminiscent of embryonic cells. Our findings provide strong evidence to propose that there are two restriction points for B cell activation: at the transition from G0 to G1 and at the transition from G1 to S phase.

Adjuvants, Immunologic↗

PubMed1992

CD1b restricts the response of human CD4-8- T lymphocytes to a microbial antigen.

Molecules encoded by the human CD1 locus on chromosome 1 (ref. 33) are recognized by selected CD4-8- T-cell clones expressing either alpha beta or gamma delta T-cell antigen receptors. The known structural resemblance of CD1 molecules to antigen-presenting molecules encoded by major histocompatibility complex (MHC) genes on human chromosome 6 (refs 3, 4, 34, 35), suggested that CD1 may represent a family of antigen-presenting molecules separate from those encoded in the MHC. Here we report that the proliferative and cytotoxic responses of human CD4-8- alpha beta TCR+ T cells specific for Mycobacterium tuberculosis can be restricted by CD1b, one of the four identified protein products of the CD1 locus. The responses of these T cells to M. tuberculosis seemed not to involve MHC encoded molecules, but were absolutely dependent on the expression of CD1b by the antigen-presenting cell and involved an antigen processing requirement similar to that seen in MHC class II-restricted antigen presentation. These results provide, to our knowledge, the first direct evidence for the proposed antigen-presenting function of CD1 molecules and suggest that the CD1 family plays a role in cell-mediated immunity to microbial pathogens.

Antigen-Presenting Cells↗

PubMed2014

Jarid2 is induced by TCR signalling and controls iNKT cell maturation.

Jarid2 is a reported component of three lysine methyltransferase complexes, polycomb repressive complex 2 (PRC2) that methylates histone 3 lysine 27 (H3K27), and GLP-G9a and SETDB1 complexes that methylate H3K9. Here we show that Jarid2 is upregulated upon TCR stimulation and during positive selection in the thymus. Mice lacking Jarid2 in T cells display an increase in the frequency of IL-4-producing promyelocytic leukemia zinc finger (PLZF)(hi) immature invariant natural killer T (iNKT) cells and innate-like CD8(+) cells; Itk-deficient mice, which have a similar increase of innate-like CD8(+) cells, show blunted upregulation of Jarid2 during positive selection. Jarid2 binds to the Zbtb16 locus, which encodes PLZF, and thymocytes lacking Jarid2 show increased PLZF and decreased H3K9me3 levels. Jarid2-deficient iNKT cells perturb Th17 differentiation, leading to reduced Th17-driven autoimmune pathology. Our results establish Jarid2 as a novel player in iNKT cell maturation that regulates PLZF expression by modulating H3K9 methylation.

Animals↗

PubMed1992

Interleukin 4 regulates induction of sialoadhesin, the macrophage sialic acid-specific receptor.

Sialoadhesin is a nonphagocytic lectin-like receptor found on a restricted population of tissue macrophages in lymphoid and hemopoietic tissues. In bone marrow, it is localized to areas of contact between the resident stromal macrophages and developing granulocytes, which together form myeloblastic clusters. Sialoadhesin is highly specific for sialylated glycoconjugates and may play a role in adhesion and trophic hemopoietic cell interactions, although its function is unknown. Resident peritoneal macrophages do not express high levels of sialoadhesin in vitro unless an inducing element found in normal mouse serum is present. The restricted in vivo location of this marker and its induction by mouse serum prompted us to examine the possible influence of various cytokines on its expression, measured by a sheep erythrocyte rosetting assay. None of the cytokines tested was able to induce sialoadhesin; however, interleukin 4 (IL-4) prevented the induction in the presence of serum. Expression of other macrophage markers was not influenced in parallel, and Western blotting showed that sialoadhesin antigen in cell lysates was selectively reduced by IL-4. Inhibition by IL-4 was dose dependent, could be blocked by antibodies to both IL-4 and the IL-4 receptor, and was overcome by increased serum concentrations. IL-4 is therefore a potent cytokine regulator of the sialic acid-specific receptor implicated in macrophage-hemopoietic cell interactions.

Animals↗

PubMed1992

Recombinant human CD40 ligand stimulates B cell proliferation and immunoglobulin E secretion.

Signaling through the cell surface molecule, CD40, is known to play an important role in the proliferation and differentiation of B lymphocytes. Using the thymoma cell line EL4, we recently identified and cloned a cDNA encoding a murine ligand for the CD40 molecule (mCD40-L) and showed that it has biological activity in vitro. A cDNA encoding a human homologue of the mCD40-L was isolated using crosshybridization techniques from an activated peripheral blood T cell library. The predicted amino acid sequence indicates that this human ligand for CD40 (hCD40-L) is a 261 amino acid type II membrane protein that exhibits 78% amino acid identity with its murine counterpart. Northern blot and FACS analyses suggest that the hCD40-L is restricted in its expression to T lymphocytes, and that it is most abundant on the CD4+ T cell subpopulation. Cells transfected with hCD40-L caused the proliferation of human tonsil B cells in the absence of costimuli and, in the presence of interleukin 4, induced immunoglobulin E secretion from purified human B cells. A comparison of the efficacy of the hCD40-L and mCD40-L in these assays is presented.

Amino Acid Sequence↗

PubMed1992

Effects of gamma-interferon and FK506 on resting B cell proliferation of New Zealand black/white F1 mice.

We examined the effects of gamma-interferon (gamma-IFN) and the new immunosuppressant FK506 on resting B cell proliferation of New Zealand black/white F1 hybrid (B/W F1) mice, an animal model of human systemic lupus erythematosus (SLE). gamma-IFN and FK506 inhibited in a dose-dependent manner both B cell proliferation and autoantibody production of resting B cells respectively. There was a synergistic interaction between gamma-IFN and FK506 in their inhibition and they did not exhibit cell cytotoxicity. This in vitro synergism of gamma-IFN and FK506 may have clinical application in that low doses of gamma-IFN and FK506 combinations may be effective to correct polyclonal B cell activation of patients with SLE.

Animals↗

PubMed2025

Genetic analysis of IFNG-AS1 implicates opposite effects to Leishmania guyanensis-cutaneous leishmaniasis: rs4913269 confers protection while rs7134599 enhances susceptibility and correlates with high plasma IL-4 and IL-10 levels.

BACKGROUND: The long non-coding RNA interferon gamma antisense-1 (IFNGAS-1) is essential for Th1 lineage specific expression of IFNG. IFN-γ is a key component cytokine in host immune response against intracellular pathogens like Leishmania. We investigated the association of two genetic variants of IFNGAS-1, rs4913269 and rs7134599, with susceptibility or protection to Leishmania guyanensis- induced cutaneous leishmaniasis (Lg-CL). METHODS: A case-control study involving 1,714 individuals (855 Lg-CL and 859 healthy controls) was conducted in the state of Amazonas, Brazil. Genotyping of rs4913269 and rs7134599 were performed using direct nucleotide sequencing and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), respectively. Plasma cytokines concentrations (IL-10, IL-12p70, IL-4, IL-1β and TNF-α) were quantified using multiplex Luminex platform. Logistic regression, linkage disequilibrium (LD), and haplotype analyses were applied to assess genetic associations and cytokine correlations. RESULTS: Individuals with the rs4913269 G/G genotype had a 46% reduced risk of developing Lg-CL, (OR adjusted for age and sex [ORadj] = 0.54; 95% CI 0.39-0.75; Pvadj = 0.0001). Carriers of the rs7134599 A/A genotype had a 130% increased risk of progression to Lg- CL (ORadj = 2.3; 95% CI, 1.6-3.4; P = 0.0001). The rs7134599 A/G genotype also showed a 52% increased risk compared to GG genotype (ORadj = 1.52, 95%CI 1.22-1.89; Pvadj = 0.0002). The rs4913269 G/G genotype was associated with lower levels of IL-10 (P = 0.05) and IL-12p70 (P = 0.009) compared to the C/C genotype. Conversely, the rs7134599 AA genotypes were correlated with higher levels of TNF-α, IL-4, IL-10 and IL-1β in comparison to the GG genotype. LD revealed independent segregation of the variants. CONCLUSIONS: The IFNG-AS1 variants rs4913269 and rs7134599 exert opposing effects on Lg-CL risk and modulate key cytokines involved in disease pathogenesis. These findings underscore the regulatory role in immune responses and increase our understanding of the immunogenetic basis of CL and support the potential IFNG-AS1 as a biomarker for susceptibility.

Humans↗

PubMed1992

Human arterial smooth muscle cells synthesize granulocyte colony-stimulating factor in response to interleukin-1 alpha and tumor necrosis factor-alpha.

Vascular smooth muscle cells (SMC) are a major cell type comprising the walls of blood vessels. We report the synthesis of granulocyte colony-stimulating factor (G-CSF) by cultured human SMC obtained from the internal mammary artery and thoracic aorta. Interleukin-1 alpha (IL-1 alpha) greatly increased in a dose-dependent manner the amount of this cytokine produced by the SMC, with tumor necrosis factor-alpha (TNF-alpha) being less effective. Newly formed G-CSF could be detected in culture supernatants within 6 hours after IL-1 alpha or TNF-alpha treatment. Northern blot analysis of SMC stimulated with IL-1 alpha and TNF-alpha showed an increase in the amount of mRNA for G-CSF as compared with control cells. Enhanced G-CSF mRNA levels were observed when SMC were treated with cycloheximide in the absence or presence of added cytokine. In vasculitis, the walls of blood vessels become inflamed as evidenced by a leucocytic infiltrate usually dominated by polymorphonuclear neutrophil leukocytes (PMNs). G-CSF is known to stimulate PMNs, and our findings raise the possibility that G-CSF made by SMC contributes to the development of vasculitis lesions.

Aorta↗

PubMed1992

Prolongation of survival of human polymorphonuclear neutrophils by granulocyte-macrophage colony-stimulating factor is caused by inhibition of programmed cell death.

In the absence of appropriate stimuli, polymorphonuclear neutrophils (PMN) undergo programmed cell death (PCD), also termed apoptosis. We show that granulocyte-macrophage colony-stimulating factor (GM-CSF), but not the chemotactic factors formyl-methionyl-leucyl-phenylalanine (FMLP), recombinant human (rh) C5a, transforming growth factor (TGF)-beta, and interleukin-8 (IL-8), or other cytokines including IL-3, IL-4, IL-6, and G-CSF, maintains viability of PMN in culture by preventing these cells from undergoing PCD. Prevention from PCD by GM-CSF was associated with induction of RNA and protein synthesis in PMN. Inhibition of RNA and protein synthesis by actinomycin-D and cycloheximide impeded the protection of apoptosis by GM-CSF. Similarly, neutralization of GM-CSF biologic activity by a specific antiserum abrogated GM-CSF-mediated inhibition of PCD.

Apoptosis↗

PubMed1992

Murine B7 antigen provides a sufficient costimulatory signal for antigen-specific and MHC-restricted T cell activation.

We have previously shown that the murine B7 (mB7) molecule, when expressed in Chinese hamster ovary cells in stable fashion, can costimulate with anti-CD3 mAb or Con A to induce T cell activation. We have now derived, by gene transfection, Chinese hamster ovary cell lines that express the I-Ad molecule, either alone or in context with mB7. We have analyzed these transfectants for their capacity to present Ag to murine CD4+ T lymphocytes. I-Ad/mB7-double transfectants were able to stimulate mixed lymphocyte reactions and to present peptide Ag to specific T cells. Chinese hamster ovary cells that expressed only the I-Ad molecule were not able to stimulate T cell proliferation in these systems. Thus, the mB7 protein is a sufficient costimulatory molecule for the physiologic, Ag-dependent/MHC-restricted activation of murine CD4+ T cells. Stimulation of T cell bulk cultures resulted predominantly in the production of IL-2 and not of IL-4. The costimulatory activity of mB7 is not, however, restricted to the IL-2-secreting subset. We have identified one IL-4-secreting T cell clone, CDC35, which is responsive to mB7 triggering. Finally, we present experiments that suggest that mB7 and peptide/MHC complexes need to be expressed on the same cell for optimal induction of T cell activation.

Animals↗

PubMed1992

Molecular interactions mediating T-B lymphocyte collaboration in human lymphoid follicles. Roles of T cell-B-cell-activating molecule (5c8 antigen) and CD40 in contact-dependent help.

In lymphoid follicles, CD4+ T lymphocytes provide contact-dependent stimuli to B cells that are critical for the generation of specific antibody responses in a process termed Th function. The CD4+ T cell-restricted surface activation protein, 5c8 Ag (T-BAM), has recently been shown to be a component of the contact-dependent helper signal to B cells. To further dissect this process, we utilized a Jurkat T cell lymphoma clone, termed D1.1, that constitutively expresses T-BAM and activates peripheral B cells to express surface CD23 in a contact-dependent mechanism that is inhibited by mAb anti-T-BAM (5c8). Similar to its effect on peripheral B cells, Jurkat D1.1 activates B cells from lymphoid organs, as well as a B cell lymphoma clone, RAMOS 266,4CN 3F10 (RAMOS 266), to up-regulate surface CD23. Interestingly, mAb to the B cell surface molecule, CD40 (mAb G28-5 and B-B20), inhibit D1.1 induced activation of RAMOS 266 and peripheral and lymphoid B cells. In contrast, mAb to CR2 or the adhesion molecules, LFA1, LFA3, or ICAM-1, have little effect. The inhibitory effect of anti-CD40 mAb on B cell activation induced by D1.1 is specific because anti-CD40 potentiates, rather than inhibits, the up-regulation of CD23 on B cells induced by rIL-4. Moreover, cross-linking CD40 molecules by anti-CD40 mAb bound to Fc gamma RII+ (CD32) L cells induces B cell CD23 expression. In vivo, T-BAM-expressing cells are CD4+ T cells that are restricted to lymphoid organs and are localized in the mantle and centrocytic zones of lymphoid follicles and the spleen periarteriolar lymphoid sheath in association with CD40+ B cells. Taken together, these data demonstrate that T-BAM on T cells and CD40 on B cells are involved in contact-dependent T-B help interactions that occur in lymphoid follicles.

Antigens, CD↗

PubMed1992

Role of antigen-specific T cell help in the generation of in vivo antibody responses. I. Antigen-specific T cell help is required to generate a polyclonal IgG1 response in anti-IgD antibody-injected mice.

A system in which injection of mice with an antibody to mouse IgD that they recognize as foreign stimulates a large, T cell-dependent IgG response was used to study whether Ag-specific T cell help is required to stimulate polyclonal (non-Ag-specific) IgG production in vivo. Igha x Ighb allotype heterozygous mice were injected with a conjugate of a foreign Ag coupled to a mAb specific for one of the two IgD allotypes expressed in these mice. This conjugate cross-links mIgD on B cells that express the recognized allotype. These cells process the conjugate and present the foreign Ag to Ag-specific T lymphocytes, which become activated. Thus, B cells of the recognized allotype can be stimulated by cross-linking of their mIgD, Ag-specific T cell help, non-Ag-specific cytokines, and non-Ag-specific contact with activated T cells. In contrast, B cells that express the Igh allotype not recognized by the Ag-anti-IgD antibody conjugate (bystander B cells) can be stimulated in this system only by non-Ag-specific cytokines and non-Ag-specific contact with activated T cells. Although both recognized and bystander B cells in conjugate-injected mice demonstrated substantial increases in size and Ia expression, only the recognized B cells were induced to synthesize DNA and to make a substantial polyclonal Ig response. Bystander B cells still failed to secrete IgG when mice were injected with an anti-IgD-Ag conjugate specific for the other Igh allotype as well as a mAb that cross-linked IgD of the bystander B cell allotype. These observations demonstrate that although non-Ag-specific cytokine and contact-mediated T cell help are sufficient to induce B cells to increase in size and Ia expression in anti-IgD antibody-injected mice, Ag-specific T cell help is required to stimulate the generation of an IgG response in these mice.

Animals↗