Biomedical subjects

H Weedon

Publications and source records attributed to H Weedon.

At least 19 recordsLinked to original sources

PubMed2007

Characterisation of a dendritic cell subset in synovial tissue which strongly expresses Jak/STAT transcription factors from patients with rheumatoid arthritis.

OBJECTIVES: To characterise the phenotype of the putative dendritic cells strongly expressing Jak3 and STAT4, which have been previously identified in the synovial tissue of patients with active rheumatoid arthritis (RA). METHODS: Synovial biopsy specimens were obtained at arthroscopy from 30 patients with active RA (42 synovial biopsies). Immunohistological analysis was performed using monoclonal antibodies to detect dendritic cell subsets, including activation markers and cytokines relevant to dendritic cell function. Co-localisation of cell surface markers and cytokines was assessed primarily using sequential sections, with results confirmed by dual immunohistochemistry and immunofluorescence with confocal microscopy. RESULTS: The dendritic cells identified in RA synovial tissue that strongly express Jak3 also strongly express STAT4 and STAT 6 and are correlated with the presence of serum rheumatoid factor. These cells are not confined to a single dendritic cell subset, with cells having phenotypes consistent with both myeloid- and plasmacytoid-type dendritic cells. The activation status of these dendritic cells suggests that they are maturing or mature dendritic cells. These dendritic cells produce IL12 as well as interferon alpha and gamma. CONCLUSIONS: The close correlation of these dendritic cells with the presence of serum rheumatoid factor, a prognostic factor for worse disease outcome, and the strong expression by these cells of components of the Jak/STAT transcription factor pathway suggest a potential therapeutic target for the treatment of RA.

Adult↗

PubMed2006

Changes in synovial tissue Jak-STAT expression in rheumatoid arthritis in response to successful DMARD treatment.

BACKGROUND: Modulation of Jak-STAT signalling may provide an effective therapeutic strategy in inflammatory arthritis (IA). OBJECTIVE: To examine the effect of successful disease-modifying antirheumatic drug (DMARD) treatment on the expression of Jak-STAT in a cohort of patients with active rheumatoid arthritis. METHODS: Synovial tissue biopsy specimens from 16 patients with active rheumatoid arthritis, taken before and after initiation of DMARD treatment, were examined for the presence of janus kinase (Jak)3, signal transducer and activator of transcription (STAT)1, STAT4 and STAT6 expression using immunohistochemistry. RESULTS: Successful treatment with DMARDs results in reduction in STAT1 expression in the lining, and STAT1 and STAT6 in the sublining of rheumatoid arthritis synovial tissue. Although the overall expression of STAT4 and Jak3 was not significantly altered by DMARD treatment, there was a significant reduction in the expression of the STAT4 and Jak3 bright cells, thought to be an activated dendritic cell subpopulation. CONCLUSION: Results show that Jak3, STAT1, STAT4 expression and STAT6 sublining expression decrease in response to successful treatment of rheumatoid arthritis with standard DMARDs. Therefore, altering the expression of these pathways may represent an alternative treatment option, either through promoting up-regulation of inhibitory pathways, or suppressing inflammatory paths.

Antirheumatic Agents↗

PubMed2005

Expression of Jak3, STAT1, STAT4, and STAT6 in inflammatory arthritis: unique Jak3 and STAT4 expression in dendritic cells in seropositive rheumatoid arthritis.

BACKGROUND: Modulation of Jak-STAT signalling may provide an effective therapeutic strategy in inflammatory arthritis. OBJECTIVE: To document Jak-STAT expression in a cohort of patients with active rheumatoid arthritis (RA), spondyloarthritis (SpA), and osteoarthritis (OA) and compare these subsets with normal synovial tissue. METHODS: Synovial tissue biopsy specimens from patients with RA, OA, and SpA and histologically normal tissue (n = 10 in each arthritis group) were examined for the presence of Jak3, STAT1, STAT4, and STAT6 expression using immunohistochemistry. Phenotyping was performed using immunohistochemistry and immunofluorescence. Clinical and serological characteristics of patients with RA expressing Jak3-STAT4 were assessed. RESULTS: STAT1, STAT4, and Jak3 protein expression was generally increased in inflammatory arthritis. In contrast, STAT6 expression was relatively heterogeneous. A subpopulation of CD1a positive dendritic cells unique to seropositive patients with RA was detected. These cells showed intense protein expression for Jak3, STAT4, and STAT6. CONCLUSION: CD1a positive dendritic cells intensely express Jak3, STAT4, and STAT6 in seropositive RA tissue and may be an alternative marker for dendritic cells in their early stages of activation as well as providing a tool for identifying RA at the level of the synovium. Jak3 inhibition may be a potential therapeutic target to prevent dendritic cell maturation in RA. STAT1 expression is increased in inflammatory arthritis, suggesting that its pro-apoptotic and anti-inflammatory effects cannot effectively counteract inflammation. STAT6 expression is heterogeneous in synovium, suggesting a possible homoeostatic role in addition to any anti-inflammatory effects.

Adult↗

PubMed2004

Factors regulating osteoclast formation in human tissues adjacent to peri-implant bone loss: expression of receptor activator NFkappaB, RANK ligand and osteoprotegerin.

Aseptic bone loss adjacent to orthopedic joint implants is a common cause of joint implant failure in humans. This study investigates the expression of key regulators of osteoclast formation, receptor activator NFkappaB (RANK), Receptor activator of NFkappaB ligand (RANKL) and osteoprotegerin (OPG), in the peri-implant tissues of patients with osteolysis compared with levels in synovial tissues from osteoarthritic and healthy subjects. Immunohistochemical studies demonstrated that significantly higher levels of RANKL protein (p<0.05) were found in the peri-implant tissues of patients with implant failure than in similar tissues from osteoarthritic and healthy subjects. In contrast, OPG protein levels were similar in all tissues. RANKL, expressed as mRNA and protein, was predominantly associated with cells containing wear particles. Dual labeling studies showed that the cells expressing RANKL protein were macrophages. In situ hybridization studies confirmed that mRNA encoding for these proteins is also expressed by cells in the peri-implant tissues. In addition, RANK mRNA was expressed in cells that contained wear particles. These findings show that abnormally high levels of RANKL are expressed in peri-implant tissues of patients with prosthetic loosening and that these abnormal levels of RANKL may significantly contribute to aseptic implant loosening.

Adult↗

PubMed2004

T cells, fibroblast-like synoviocytes, and granzyme B+ cytotoxic cells are associated with joint damage in patients with recent onset rheumatoid arthritis.

OBJECTIVE: To determine immunohistological markers in synovial tissue of patients with early rheumatoid arthritis (RA) which are associated with unfavourable disease outcome. METHODS: Synovial tissue was obtained from 36 patients with RA within 1 year after the initial symptoms and before starting disease modifying antirheumatic drug treatment. Clinical, laboratory, and radiological assessments (Larsen score) were performed at the time of the biopsy and at the end of follow up (mean 58 months, range 38-72). Immunohistological analysis was performed to detect T cells, B cells, plasma cells, fibroblast-like synoviocytes (FLS), macrophages, and granzyme B+ cytotoxic cells. The sections were evaluated by digital image analysis. RESULTS: Patients were divided into two groups based upon the radiological progression per year of follow up: group I with mild progression (n = 20; Larsen <2 points/year); group II with more severe progression (n = 16; Larsen > or =2 points/year). Regression analysis with a univariate model showed that the numbers of granzyme B+ cytotoxic cells (relative risk (RR) = 12, p = 0.003), T cells (RR = 11, p = 0.013), and FLS (RR = 10, p = 0.020) discriminated between groups I and II. A multivariate model demonstrated that the numbers of T cells (RR = 1.2, p = 0.015) and FLS (RR = 1.4, p = 0.013) were independent discriminators between groups I and II. CONCLUSION: The numbers of granzyme B+ cytotoxic cells, T cells, and FLS in synovial tissue of patients with RA are related to the severity of joint damage. The data suggest a pathogenetic role for these cells in the process of joint damage.

Adult↗

PubMed2003

Osteoprotegerin expression in synovial tissue from patients with rheumatoid arthritis, spondyloarthropathies and osteoarthritis and normal controls.

OBJECTIVES: To demonstrate the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor kappaB ligand (RANKL) in synovial tissue from rheumatoid arthritis (RA) patients, establish the cell lineage expressing OPG and compare the expression of OPG in RA, spondyloarthropathies, osteoarthritis and normal synovial tissue. METHODS: Synovial biopsy specimens were obtained at arthroscopy from 16 RA and 12 spondyloarthropathy patients with active synovitis of a knee joint, six RA patients with no evidence of active synovitis, 10 patients with osteoarthritis and 18 normal subjects. Immunohistological analysis was performed using monoclonal antibodies (mAb) to detect OPG and RANKL expression. In addition, dual immunohistochemical evaluation was performed with lineage-specific monoclonal antibodies (macrophages, fibroblasts and endothelial cells) and OPG to determine the cell lineages expressing OPG. The sections were evaluated by computer-assisted image analysis and semiquantitative analysis. RESULTS: Two patterns of OPG expression were seen, one exclusively in endothelial cells and one expressed predominantly in macrophages in the synovial lining layer. Both patterns of OPG staining could be blocked with excess recombinant OPG. Endothelial and synovial lining expression of OPG was seen in all synovial tissues except those from patients with active RA. In contrast, RANKL expression was seen predominantly in synovial tissue from patients with active disease, mainly in sublining regions, particularly within areas of lymphocyte infiltration. CONCLUSIONS: OPG expression on macrophage type synovial lining cells as well as endothelial cells is deficient in RA patients with active synovitis, in contrast to that seen in spondyloarthropathy patients with active synovitis. This deficiency in OPG expression in the inflamed joint of RA patients may be important in the development of radiologically defined joint erosions.

Acute Disease↗

PubMed2003

Microarchitecture and protective mechanisms in synovial tissue from clinically and arthroscopically normal knee joints.

BACKGROUND: Synovial biopsies are used to study synovial immunopathology and are increasingly applied for the evaluation of new therapeutic strategies in chronic arthritis. Therefore, it is essential to be informed on the complete spectrum of synovial immunopathology. OBJECTIVE: To describe the cellular content, cytokine and cell adhesion molecule expression in synovial tissue from clinically and arthroscopically normal knees. METHODS: Synovial tissue was obtained from 20 normal subjects at the time of knee joint arthroscopy for unexplained knee pain. Tissue sections were studied for basic histopathology and for a range of cell surface markers, cytokines, and cell adhesion molecules by immunoperoxidase staining. Stained sections were evaluated by semiquantitative scoring and digital image analysis. RESULTS: Normal synovial tissue is composed predominantly of fibrofatty areolar tissue, with a variable thickness of intimal lining, composed of both CD68 positive macrophages and CD55 positive fibroblast-like synoviocytes. Interleukin 1 receptor antagonist (IL1Ra) was frequently detected in the synovial membrane of normal subjects (mean (SD) integrated optical density (IOD)=3809.6 (3893.9)), but both tumour necrosis factor alpha (TNFalpha) and interleukin 1beta (IL1beta) were rarely detected. In addition, cell adhesion molecules were rarely detected in the normal synovial membrane, with the exception of intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Osteoprotegerin (OPG) expression was abundant on synovial lining macrophages (mean (SD) IOD=5276 (4716) as well as endothelial cells (mean (SD) IOD=557 (226)), but receptor activator of nuclear factor kappa ligand (RANKL) expression was rarely seen. CONCLUSIONS: The normal synovial membrane has a variable architecture, including thickness of the lining and the subintimal cell infiltrate, with little inflammatory cytokine production or expression of cell adhesion molecules. The excess of OPG expression over RANKL and IL1Ra over IL1 may be important for protection against joint damage

Adolescent↗

PubMed2002

Macrophage migration inhibitory factor in rheumatoid arthritis: clinical correlations.

OBJECTIVE: Cytokines play an important role in the pathology of rheumatoid arthritis (RA). Macrophage migration inhibitory factor (MIF) is a cytokine with a broad spectrum of actions, including induction of monocyte tumour necrosis factor alpha (TNF-alpha). Evidence of the expression and proinflammatory activity of MIF has recently been demonstrated in RA synovium and in animal models of RA. We wished to assess the relationship between MIF expression in synovium and clinical disease. METHODS: Computer-assisted analysis of the cytokine content of arthroscopically obtained biopsies of RA synovium, using paired samples from eight patients with active and inactive/treated disease, was compared with documented clinical parameters. RESULTS: Synovial MIF immunostaining correlated strongly with disease activity as measured by CRP concentration. Reductions in clinical disease parameters, including CRP, tender and swollen joint counts, were accompanied by significant reductions in synovial MIF. Synovial TNF-alpha, transforming growth factor beta (TGF-beta) and interleukin (IL) 10 also showed a significant reduction in association with reduced disease activity, while IL-1 beta and IL-1 receptor agonist did not. CONCLUSION: The correlation of synovial MIF with disease activity corroborates existing evidence of the role of this cytokine in RA. The demonstration that only MIF and TNF-alpha show significant variation in synovial cytokine content with clinical remission suggests that MIF is an important member of the cytokine hierarchy in RA.

Aged↗

PubMed2002

Receptor activator NF-kappaB ligand (RANKL) expression in synovial tissue from patients with rheumatoid arthritis, spondyloarthropathy, osteoarthritis, and from normal patients: semiquantitative and quantitative analysis.

OBJECTIVES: To compare receptor activator of NF-kappaB ligand (RANKL) production in the synovial tissue from patients with active rheumatoid arthritis (RA), inactive RA, spondyloarthropathies (SpA), osteoarthritis, and from normal subjects. In addition, to establish the cell lineages expressing RANKL in these tissues. METHODS: Immunohistological analysis of frozen synovial tissue biopsy specimens was performed using a monoclonal antibody (mAb) to detect RANKL. Sections were evaluated by computer assisted image analysis and semiquantitative analysis to compare RANKL expression between groups. Dual and sequential labelling with mAb RANKL and cell lineage specific monoclonal antibodies were used to determine the types of cells expressing RANKL. RESULTS: Higher levels of RANKL were expressed in tissues from patients with active RA and SpA than in tissues from patients with inactive RA, osteoarthritis, and from normal subjects. RANKL protein was associated with CD3 antigen-positive lymphocytes and some macrophages. RANKL was predominantly associated with activated, memory T cells (CD45Ro positive cells) in patients with active RA and spondyloarthropathy (SpA). CONCLUSIONS: The highest levels of RANKL were detected in patients with RA with active synovitis and in some patients with SpA. An increase in RANKL in the inflamed joint of patients with RA, produced by infiltrating activated T cells and macrophages, is likely to be an important cause of joint erosions in RA.

Adult↗

PubMed2001

Association of clinical, radiological and synovial immunopathological responses to anti-rheumatic treatment in rheumatoid arthritis.

OBJECTIVES: To compare immunohistochemical scoring with clinical scoring and radiology for the assessment of rheumatoid arthritis (RA) disease activity, synovial tissue (ST) biopsied arthroscopically was assessed from 18 patients before and after commencement of disease-modifying anti-rheumatic drug (DMARD) therapy. METHODS: Lymphocytes, macrophages, differentiated dendritic cells (DC), vascularity, tumour necrosis factor (TNF) alpha and interleukin-1beta levels were scored. Clinical status was scored using the American College of Rheumatology (ACR) core set and serial radiographs were scored using the Larsen and Sharp methods. Histopathological evidence of activity included infiltration by lymphocytes, DC, macrophages, tissue vascularity, and expression of lining and sublining TNFalpha. These indices co-varied across the set of ST biopsies and were combined as a synovial activity score for each biopsy. RESULTS: The change in synovial activity with treatment correlated with the ACR clinical response and with decreased radiological progression by the Larsen score. The ACR response to DMARD therapy, the change in synovial activity score and the slowing of radiological progression were each greatest in patients with high initial synovial vascularity. CONCLUSIONS: The data demonstrate an association between clinical, radiological and synovial immunopathological responses to anti-rheumatic treatment in RA. High ST vascularity may predict favourable clinical and radiological responses to treatment.

Aged↗

PubMed2001

Treatment-induced remission in rheumatoid arthritis patients is characterized by a reduction in macrophage content of synovial biopsies.

OBJECTIVES: To document the change in synovial membrane macrophage and T-lymphocyte content in rheumatoid arthritis (RA) patients who achieve remission induced by disease-modifying anti-rheumatic drugs (DMARDs). METHODS: Arthroscopic synovial biopsies were taken from four to seven sites around a knee joint in 13 patients with RA before and at regular intervals after commencing treatment with a DMARD. The cellular content of synovial membrane biopsies taken at regular intervals for a period of up to 3 yr after commencing treatment was quantitated by routine histopathology and immunohistochemical labelling with anti-macrophage (CD68) and anti-T lymphocyte (UCHL-1) antibodies. Synovial biopsies were quantitated with a validated semiquantitative scoring system and video image analysis. RESULTS: Nine patients obtained clinical remission, as defined by American College of Rheumatology (ACR) criteria. The changes that occurred in the synovial biopsies included a reduction in lining layer thickness, reduced vascularity and cellular infiltrate. The most significant reduction in cellular infiltrate was in the lining layer macrophages, with less dramatic change in the subintimal macrophage infiltrate. Although there was a reduction in CD45 Ro-positive T lymphocytes in the synovial membranes of patients who attained ACR-defined disease remission, it was less significant than the reduction in macrophage content of the synovial membranes and tended to plateau at a reduced level of T-cell infiltration. CONCLUSIONS: Remission in RA patients is characterized by a predominant reduction in macrophage content of the synovial membrane, suggesting that current DMARDs may target this cell and its inflammatory mediators.

Aged↗

PubMed2001

Successful treatment of rheumatoid arthritis is associated with a reduction in synovial membrane cytokines and cell adhesion molecule expression.

OBJECTIVE: To investigate the change in synovial membrane cytokine content and cell adhesion molecule expression in sequential biopsies from the same knee joint of patients with rheumatoid arthritis, before and following anti-rheumatic drug treatment and to assess the relationship of these changes with clinical responses to the drug treatment. METHODS: A selected group of patients with rheumatoid arthritis, some of whom had achieved a disease remission based on American College of Rheumatology (ACR) criteria, were included in this study. Sequential synovial biopsies obtained before and throughout the treatment period were studied by immunohistochemical labelling techniques for the cellular content, production of a range of pro- and anti-inflammatory cytokines and the expression of cell adhesion molecules. The staining was quantitated using computer-assisted digital image analysis. RESULTS: There was a decrease in tumour necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta) production in the synovial membrane lining and sublining of all patients who responded to treatment. The changes in IL-1 receptor antagonist production were variable. Paradoxically, there was a trend to decreased synovial membrane production of the anti-inflammatory cytokines, IL-10 and transforming growth factor-beta (TGFbeta), while IL-4 was not detectable in any of the synovial membrane biopsies. A significant reduction in the density and total amount of E-selectin expression in the synovial membrane was seen. Similarly, intercellular adhesion molecule-1 (ICAM-1) expression in the lining and sublining was decreased in those patients who had a significant clinical response to drug treatment or attained disease remission. There were no consistent or significant changes seen in the expression of other cell adhesion molecules in the synovial membranes of these patients. CONCLUSIONS: Successful drug treatment of rheumatoid arthritis patients is characterized at the synovial membrane level by a decrease in TNFalpha, IL-10 and TGFbeta production. Some (E-selectin and ICAM-1) but not all (P-selectin, VCAM-1, PECAM-1) cell adhesion molecules are modulated in patients who respond clinically to drug treatment. E-selectin and ICAM-1 may be important targets for the development of future drug treatments for rheumatoid arthritis.

Aged↗

PubMed2001

Measurement of cytokine and adhesion molecule expression in synovial tissue by digital image analysis.

OBJECTIVE: Digital image analysis (DIA) offers the opportunity to quantify the stained area and staining intensity when synovial tissue (ST) is investigated by immunohistochemical analysis. This study aimed at determining the sensitivity of DIA compared with semiquantitative analysis (SQA). METHODS: Paired ST samples were obtained from the knee joint of 10 patients with rheumatoid arthritis (RA) with active disease and after follow up when complete clinical remission was achieved. ST samples of 10 subjects with non-inflammatory knee pain served as controls. Immunohistochemistry with antibodies against interleukin 1beta (IL1beta) and vascular cell adhesion molecule 1 (VCAM-1) was applied using two staining protocols with 3-amino-9-ethylcarbazole (AEC) or p-diethylaminobenzaldehyde (DAB) as dye. All sections were analysed semiquantitatively (0-4) and DIA of up to a maximum of 60 high power fields (HPF). The average integrated optical density was calculated as the product of the stained area (corrected for total tissue area) and the optical density. RESULTS: Both SQA and DIA enabled the assessment of differences in IL1beta and VCAM-1 expression between ST from active RA, RA in remission, and controls. SQA and DIA showed excellent correlations (IL1beta rs=0.867; p<0.0001: VCAM-1 rs=0.828; p<0.0001). A limited analysis of one region with six HPF still allowed adequate discrimination compared with an extended analysis of three regions with a total of 60 HPF. In general, the red dye (AEC) resulted in better discrimination than the brown (DAB) staining. CONCLUSION: DIA offers a reliable, reproducible, and sensitive analysis of ST sections stained for cytokines and adhesion molecules.

Adult↗

PubMed2000

The development of clinical signs of rheumatoid synovial inflammation is associated with increased synthesis of the chemokine CXCL8 (interleukin-8).

Paired synovial tissue samples were obtained from both clinically uninvolved (CU) and clinically involved (CI) knee joints of eight rheumatoid arthritis (RA) patients. In addition, biopsies were taken from five control subjects. We observed the expression of the chemokines CXCL8, CXCL9, CXCL10, CCL2 and CCL4 in CI and CU joints of RA patients. In particular, CXCL8 protein levels were specifically increased in CI joints compared with CU joints, which was confirmed by immunohistochemistry and in situ hybridization.

Arthritis, Rheumatoid↗

PubMed1999

Macrophage migration inhibitory factor in rheumatoid arthritis: evidence of proinflammatory function and regulation by glucocorticoids.

OBJECTIVE: Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine whose involvement in tumor necrosis factor alpha (TNFalpha) synthesis and T cell activation suggests a role in the pathogenesis of rheumatoid arthritis (RA). Antagonism of MIF is associated with marked inhibition of animal models of RA. Uniquely, MIF is inducible by low concentrations of glucocorticoids. We sought to investigate the expression of MIF in RA synovial tissue. METHODS: MIF was demonstrated in human RA synovium by immunohistochemistry, flow cytometry, enzyme-linked immunosorbent assay (ELISA), and reverse transcription-polymerase chain reaction (RT-PCR). Regulation of MIF expression was investigated by treatment of cultured fibroblast-like synoviocytes (FLS) with interleukin-1beta (IL-1beta), TNFalpha, or interferon-gamma (IFNgamma), and dexamethasone (DEX). Mononuclear cell TNFalpha release after exposure to FLS-conditioned medium was measured by ELISA. RESULTS: MIF was present in RA synovial lining CD14+ macrophages and FLS. Constitutive MIF messenger RNA (mRNA) expression was demonstrated by RT-PCR of RNA from unstimulated cultured RA FLS, which also released abundant MIF. Serum, synovial fluid, and FLS intracellular MIF were significantly higher in RA patients than in controls. Synoviocyte MIF was not increased by IL-1beta, TNFalpha, or IFNgamma. In contrast, DEX 10(-7)M significantly reduced synoviocyte MIF, while DEX 10(-10)-10(-12)M induced a significant increase in MIF and MIF mRNA. Peripheral blood mononuclear cell TNFalpha release was induced by culture in RA FLS-conditioned medium, and this induction was significantly abrogated by monoclonal anti-MIF antibody, suggesting that MIF is an upstream regulator of TNFalpha release. CONCLUSION: These data represent the first demonstration of the cytokine MIF in human autoimmune disease and suggest MIF as a potential therapeutic target in RA.

Aged↗

PubMed1999

Cytokines and cell adhesion molecules in musculoskeletal disorders.

This paper reviews the cytokine profiles and various cell adhesion molecules expressed in the more common inflammatory joint conditions such as rheumatoid arthritis, psoriatic arthritis, the spondyloarthropathies (Reiter's syndrome, ankylosing spondylitis), as well as systemic lupus erythematosus, systemic sclerosis, Sjögren's syndrome, giant cell arteritis and polymyositis. Knowledge of the broad range of cytokines produced in these conditions and the expression of cell adhesion molecules that result from cytokine production will assist in the understanding of the pathogenesis of these conditions and may lead to new therapeutic interventions.

Journal Article↗

PubMed1998

Interleukin 2 receptor regulation and IL-2 function in the human infant.

IL-2 receptor is expressed at low levels on adult blood lymphocytes, and at lower levels on cord blood cells. IL-2 receptor alpha and beta chain expression increases gradually from 0-18 months of age. The level of soluble CD25 (IL-2 receptor alpha chain) has been reported to be elevated in cord blood. Quantitative RT-PCR showed that adult cells express 10 times as much CD25 mRNA as cord cells. Cord plasma showed only a marginal ability to strip CD25 from the membrane. To assess the functional consequences of low IL-2 receptor expression, cord and adult cells were activated in vitro. The response was stimulus-dependent, but cord cells upregulated CD25 readily. Cord and adult cells proliferated in an IL-2-dependent assay to a similar extent. Infants suffering acute infection showed marginally higher levels of membrane CD25 expression than infants without overt infection. Thus neonatal and infant lymphocytes express lower levels of IL-2 receptors than adult cells, reflecting lower mRNA concentrations at least for CD25; they are able to up-regulate receptors in response to in vitro stimulation and are able to respond in vitro to IL-2-dependent stimulation; however in vivo there may be a dampening down of the IL-2 system in infancy.

Adult↗

PubMed1997

The antigen receptor complex on cord B lymphocytes.

The neonatal immune system responds to a restricted range of antigens, producing largely IgM antibody of low affinity. Comparison of the components of the B-cell antigen receptor complex shows significantly elevated membrane levels of IgM in neonatal B cells, compared with adult cells. CD79, which acts as the signal transducer for membrane immunoglobulin, is elevated in parallel with IgM, while IgD is elevated to a lesser degree. CD19, CD21, CD22 and CD81, which are all involved in transmitting activation signals when immunoglobulin is engaged, are not elevated. CD32, which is involved in negative regulation of activation, is present at reduced levels on cord B cells. The elevation of B-cell membrane IgM persists during infancy. Neonatal B cells respond in vitro to interleukin-4 (IL-4) by further elevation of membrane IgM levels. The elevated level of membrane IgM may make neonatal B cells easier to trigger by low concentrations of antigen, but in vitro activation and immunoglobulin modulation experiments did not show significant differences between cord and adult B-cell responses to anti-IgM.

Adult↗