Comparison of blood and synovial fluid th17 and novel peptidase inhibitor 16 Treg cell subsets in juvenile idiopathic arthritis

OBJECTIVE

Early recognition and treatment of juvenile idiopathic arthritis (JIA) can prevent joint damage and minimize side effects of medication. The balance between proinflammatory and antiinflammatory mechanisms is known to be important in JIA, and we therefore investigated T cell subsets including Th cells, autoaggressive Th17 cells, and regulatory T cells (Treg), including a novel Treg subset in peripheral blood (PB) and synovial fluid (SF) of patients with JIA.

METHODS

Fifty children with JIA were enrolled in our study. Frequency, phenotype, and function of T lymphocytes in PB and SF were characterized using flow cytometry. Migration capabilities of PB and SF cells were compared.

RESULTS

Synovial T cells showed different phenotype and function compared with PB T cells, with an increased proportion of memory T cells, expression of CCR4, CCR5, CXCR3, interleukin 23R, and an increased ratio of Th17 to Treg. Although Treg were increased in SF compared with the PB, we found a significant decrease in the numbers of peptidase inhibitor 16 (PI16)+ Treg in active joints compared with peripheral blood. Coexpression of CCR4 and CCR6 was reduced on PI16+ Treg in PB and SF of patients with JIA compared with healthy children, however the ability of these cells to migrate toward their ligands was unaffected.

CONCLUSION

This is a comprehensive characterization of novel PI16+ Treg and Th17 cells in matched blood and synovial fluid samples of patients with JIA. Despite an increased number of Treg within the inflamed joint, lower numbers of PI16+ Treg but high numbers of Th17 cells might contribute to the inability to control disease.

PI16 is expressed by a subset of human memory Treg with enhanced migration to CCL17 and CCL20

The peptidase inhibitor PI16 was shown previously by microarray analysis to be over-expressed by CD4-positive/CD25-positive Treg compared with CD4-positive/CD25-negative Th cells. Using a monoclonal antibody to the human PI16 protein, we found that PI16-positive Treg have a memory (CD45RO-positive) phenotype and express higher levels of FOXP3 than PI16-negative Treg. PI16-positive Treg are functional in suppressor assays in vitro with potency similar to PI16-negative Treg. Further phenotyping of the PI16-positive Treg revealed that the chemokine receptors CCR4 and CCR6 are expressed by more of the PI16-positive/CD45RO-positive Treg compared with PI16-negative/CD45RO-positive Treg or Th cells. PI16-positive Treg showed enhanced in vitro migration towards the inflammatory chemokines CCL17 and CCL20, suggesting they can migrate to sites of inflammation. We conclude that PI16 identifies a novel distinct subset of functional memory Treg which can migrate to sites of inflammation and regulate the pro-inflammatory response at those sites.

Expression of Toll-like receptors by neonatal leukocytes

The immune system of neonates is poorly developed; this increases the susceptibility of neonates to infection. For neonates to counter infection effectively, they first need to recognize the presence of pathogens. Toll-like receptors (TLR) are a family of pattern recognition receptors that alert the host to the presence of invading pathogens. To determine whether differences in TLR expression by leukocytes compensate for immunologic immaturity in neonates, TLR expression by monocytes and T lymphocytes from adults and neonates was compared. Expression of TLR1, TLR2, TLR3, TLR4, TLR8 and TLR9 by monocytes and T lymphocytes was detected with antibodies by flow cytometry. TLR1, TLR2, TLR3, TLR4, TLR8 and TLR9 expression by monocytes was detected in adults and neonates. TLR2, TLR3, TLR4, TLR8 and TLR9 expression by T lymphocytes was detected in adults and neonates. Monocytes and T lymphocytes from neonates are capable, like adults, of recognizing the presence of pathogens through TLR.

Toll-like receptors

Toll-like receptors are a family of transmembrane receptors responsible for recognition and initiation of a response to invading microbes by the immune system. As part of the innate immune system, Toll-like receptors recognise pathogen-associated molecular patterns, highly conserved components that are essential to microbial function. Some of ten toll-like receptors identified in humans are able to recognise several pathogen-associated molecular patterns.

Conservation of leukocyte cell surface proteins: implications for the generation of monoclonal antibodies against newly identified leukocyte cell surface proteins

The availability of mouse monoclonal antibodies has been integral to the classification of human leukocyte cell surface proteins under the "Cluster of Differentiation" or "CD" nomenclature system. The sequencing of the human genome has identified many more proteins that have characteristics similar to the known leukocyte cell surface proteins, but which have not so far been identified using monoclonal antibodies. One factor that may have limited the generation of monoclonal antibodies to some of these proteins is the high level of sequence conservation between the mouse and human proteins, in particular in the extracellular regions that are recognized by most of the widely used antibodies. An alternative approach is to use a more distant species, such as chickens, for the generation of antibody reagents. Here we compare the extent of amino acid differences in the protein CD molecules expressed by human leukocytes and their mouse and chicken homologs. The analysis confirms that the human proteins are more similar to the mouse homologs than the chicken homologs. The results indicate that chicken antibodies have the potential to be used as an alternative to mouse reagents where human-mouse sequence conservation is high.

Improved antigen binding by a CD20-specific single-chain antibody fragment with a mutation in CDRH1

We have prepared single-chain immunoglobulin Fv fragments from the CD20-specific hybridoma HB13d. One scFv clone demonstrated strong binding to a CD20-derived peptide by ELISA and to CD20-positive cells by flow cytometry, a second had reduced binding, and a third clone did not bind the target antigen. Sequence analysis showed that all three constructs contained shared and unique amino acid changes when compared to the nearest germline match. Molecular modelling of the scFv variants revealed that several of the mutations are located in regions predicted to contact antigen, including a mutation in the heavy chain CDR1 of the strongest binding scFv construct. No similar mutation is present in the highly conserved protein sequences of a number of CD20-specific monoclonal antibodies. BIACORE analysis demonstrated that the mutated scFv had approximately three-fold greater antigen-binding activity than another clone. Competition studies showed that the scFv is able to compete with intact CD20 monoclonal antibody for binding to the target antigen. The improved antigen binding of this scFv will permit the construction of novel CD20-specific reagents for the therapy of lymphomas.

Characterisation of the protein composition of peripheral blood mononuclear cell microsomes by SDS-PAGE and mass spectrometry

Approximately 340 leucocyte plasma membrane proteins have been characterised by the eight Human Leucocyte Differentiation Antigen workshops held between 1982 and 2004, based primarily on their reactivity with monoclonal antibodies. The human genome is predicted to encode approximately 34,000 cDNA transcripts, of which between 15% and 20% are predicted to contain one or more transmembrane helices. We have used SDS-PAGE separation coupled with mass spectrometry-based peptide mass tag identification to identify novel plasma membrane proteins in microsome preparations prepared from mononuclear cells obtained from human peripheral blood. A total of 361 distinct proteins were identified in a single preparation, including 37 known leucocyte plasma membrane proteins, 27 potential novel plasma membrane proteins whose expression on PBMC is poorly characterised, and 51 other proteins for which the subcellular location could not be determined. Expression analysis using cDNA panels indicates that several of these novel plasma membrane proteins are differentially expressed in lymphocyte subsets. These results show that previously unidentified lymphocyte plasma membrane proteins can be identified using this approach.

Expression of toll-like receptors on B lymphocytes

Toll-like receptors (TLRs) are a family of trans-membrane receptors that play an important role in the innate immune system. Most studies examining the cellular expression of TLRs on immune cells have focussed on neutrophils, monocytes and dendritic cells, but there is little evidence of TLRs being expressed on lymphocytes. Using 3-colour flow cytometry, expression of TLR-1, TLR-2, TLR-3, TLR-4, and TLR-9 on peripheral blood lymphocyte populations was determined. Further examination of TLRs on CD5- and CD5+ CD19+ B cell subsets was performed. The binding of TLR1 and TLR9 antibodies was detected on 15-90% of resting B cells, but not on resting T-cells. The higher expression of TLR1 and TLR9 on CD5+ B cells compared to CD5- B cells may reflect the role of B1 cells in more primitive, less specific antibody responses.

New resistance mechanism in Helicoverpa armigera threatens transgenic crops expressing Bacillus thuringiensis Cry1Ac toxin

In Australia, the cotton bollworm, Helicoverpa armigera, has a long history of resistance to conventional insecticides. Transgenic cotton (expressing the Bacillus thuringiensis toxin Cry1Ac) has been grown for H. armigera control since 1996. It is demonstrated here that a population of Australian H. armigera has developed resistance to Cry1Ac toxin (275-fold). Some 70% of resistant H. armigera larvae were able to survive on Cry1Ac transgenic cotton (Ingard) The resistance phenotype is inherited as an autosomal semidominant trait. Resistance was associated with elevated esterase levels, which cosegregated with resistance. In vitro studies employing surface plasmon resonance technology and other biochemical techniques demonstrated that resistant strain esterase could bind to Cry1Ac protoxin and activated toxin. In vivo studies showed that Cry1Ac-resistant larvae fed Cy1Ac transgenic cotton or Cry1Ac-treated artificial diet had lower esterase activity than non-Cry1Ac-fed larvae. A resistance mechanism in which esterase sequesters Cry1Ac is proposed.

In silico evaluation of two mass spectrometry-based approaches for the identification of novel human leukocyte cell-surface proteins

The identification and quantitation of cell-surface proteins expressed by leukocytes currently use the wide availability of monoclonal antibodies (mAb) in immunohistochemical and flow cytometric assays. Presently, approximately 400 such proteins have been characterized; however, analysis of the completed human genome sequence indicates that it may contain several thousand as-yet unidentified molecules, which may be expressed on the leukocyte cell surface. Recent advances in protein isolation and analysis using mass spectrometry illustrate that it is now feasible to identify the protein composition of a complex sample such as a plasma membrane extract. Such an approach may be useful for the identification of the cell-surface proteins that have not been identified using mAb techniques. Here, we detail the results of an in silico evaluation of the peptides isolated using two methods used to label plasma membrane proteins to determine whether these methods are suitable for the identification of known leukocyte cell-surface proteins by mass spectrometry. The labeling of cell-surface proteins before isolation and characterization is a valuable means of differentiating between plasma membrane and internal membrane proteins The results indicate that although the majority of cell-surface proteins can be identified using either of the approaches, others known to be important diagnostically and/or therapeutically would not be identified using either approach. The implication of this for the use of these techniques in the discovery of new leukocyte cell-surface proteins is discussed.

Detection of low-abundance membrane markers by immunofluorescence—a comparison of alternative high-sensitivity methods and reagents

The analysis of membrane molecules using antibodies detected by immunofluorescence staining and flow cytometry is used widely in research and diagnostic immunology. Conventional staining techniques readily detect molecules present at concentrations of around 2000 molecules per cell, but some molecules are expressed and function at much lower abundance. We described previously a method for the detection of molecules present at 100 molecules per cell or less based on the use of phycoerythrin as the fluorophore, a three-layer amplification process, and careful selection of available reagents. In recent years, a number of new reagents, fluorophores and kits, have become available, some of them intended for high-sensitivity applications. In this paper, a number of these reagents have been compared with the published method. While some of the reagents gave variable results or high nonspecific staining in our hands, several reagents were comparable with the published method. Furthermore, the new fluorophores allow improved simultaneous detection of two low-abundance markers.

Chimeric receptors with 4-1BB signaling capacity provoke potent cytotoxicity against acute lymphoblastic leukemia

To develop a therapy for drug-resistant B-lineage acute lymphoblastic leukemia (ALL), we transduced T lymphocytes with anti-CD19 chimeric receptors, consisting of an anti-CD19 single-chain variable domain (reactive with most ALL cases), the hinge and transmembrane domains of CD8alpha, and the signaling domain of CD3zeta. We compared the antileukemic activity mediated by a novel receptor ('anti-CD19-BB-zeta') containing the signaling domain of 4-1BB (CD137; a crucial molecule for T-cell antitumor activity) to that of a receptor lacking costimulatory molecules. Retroviral transduction produced efficient and durable receptor expression in human T cells. Lymphocytes expressing anti-CD19-BB-zeta receptors exerted powerful and specific cytotoxicity against ALL cells, which was superior to that of lymphocytes with receptors lacking 4-1BB. Anti-CD19-BB-zeta lymphocytes were remarkably effective in cocultures with bone marrow mesenchymal cells, and against leukemic cells from patients with drug-resistant ALL: as few as 1% anti-CD19-BB-zeta-transduced T cells eliminated most ALL cells within 5 days. These cells also expanded and produced interleukin-2 in response to ALL cells at much higher rates than those of lymphocytes expressing equivalent receptors lacking 4-1BB. We conclude that anti-CD19 chimeric receptors containing 4-1BB are a powerful new tool for T-cell therapy of B-lineage ALL and other CD19+ B-lymphoid malignancies.

Tolerization as a tool for generating novel monoclonal antibodies

Standard hybridoma production involves the fusion of spleen cells from an immunized mouse with a non-secretory murine myeloma cell line. While this technology has provided numerous reagents that are highly valuable, demand is now increasing for monoclonal antibodies which can distinguish between closely related antigens. Induction of tolerance towards common antigens enables the recovery of high-specificity reagents that have previously proved elusive. This review details a number of strategies using either complex protein mixtures or purified proteins as tolerogens and subsequent immunization with a closely related immunogen.

Antibody against CD20 in patients with B cell malignancy

Cancer patients may make antibodies against antigens on the surface of their malignant cells due either to the expression of unique antigens or to dysregulated responses to self antigens. Patients with B cell malignancy frequently produce autoantibodies and may therefore be a source of immunoglobulin genes for the production of phage display antibody libraries directed against tumour-associated antigens. Patients with autoimmune disease have circulating antibodies against lymphocyte surface antigens, and may also provide a good starting point for the production of a library of lymphocyte-reactive antibody structures. In this study, plasma and serum samples from patients with B cell malignancy or Sjogren's syndrome and from healthy controls were screened for antibodies against the B cell membrane antigens CD20. While the majority of samples showed very low reactivity, some individuals did show significant and reproducible binding to CD20. To identify a good donor for library construction, it would be advisable to screen donors for antibody against the antigens of interest.

Increased yield and activity of soluble single-chain antibody fragments by combining high-level expression and the Skp periplasmic chaperonin

The success of recombinant antibody fragments as diagnostic reagents and therapeutic agents depends on the availability of sufficient functional material. We have produced a bacterial expression vector that combines high-level expression driven by a modified Shine-Dalgarno sequence with the periplasmic chaperonin Skp. Using this vector, we are able to obtain higher yields of soluble antibody fragments from cultures without the need for supplementation of the culture medium during expression. The fragments produced in the presence of the Skp show improved antigen binding activity compared to when the chaperonin is absent.

Novel control motif cluster in the IgH delta-gamma 3 interval exhibits B cell-specific enhancer function in early development

The majority of the human Ig heavy chain (IgH) constant (C) region locus has been cloned and mapped. An exception is the region between C delta and C gamma 3, which is unstable and may be a recombination hot spot. We isolated a pBAC clone (pHuIgH3'delta-gamma 3) that established a 52-kb distance between C delta and C gamma 3. Sequence analysis identified a high number of repeat elements, explaining the instability of the region, and an unusually large accumulation of transcription factor-binding motifs, for both lymphocyte-specific and ubiquitous transcription activators (IKAROS, E47, Oct-1, USF, Myc/Max), and for factors that may repress transcription (Delta EF1, Gfi-1, E4BP4, C/EBP beta). Functional analysis in reporter gene assays revealed the importance of the C delta-C gamma 3 interval in lymphocyte differentiation and identified independent regions capable of either enhancement or silencing of reporter gene expression and interaction with the IgH intron enhancer E mu. In transgenic mice, carrying a construct that links the beta-globin reporter to the novel delta-gamma 3 intron enhancer (E delta-gamma 3), transgene transcription is exclusively found in bone marrow B cells from the early stage when IgH rearrangement is initiated up to the successful completion of H and L locus recombination, resulting in Ab expression. These findings suggest that the C delta-C gamma 3 interval exerts regulatory control on Ig gene activation and expression during early lymphoid development.

Antibody Repertoires of Four- and Five-Feature Translocus Mice Carrying Human Immunoglobulin Heavy Chain and κ and λ Light Chain Yeast Artificial Chromosomes

We have produced mice that carry the human Ig heavy (IgH) and both κ and λ light chain transloci in a background in which the endogenous IgH and κ loci have been inactivated. The B lymphocyte population in these translocus mice is restored to about one-third of normal levels, with preferential (3:1) expression of human λ over human κ. Human IgM is found in the serum at levels between 50 and 400 μg/ml and is elevated following immunization. This primary human Ab repertoire is sufficient to yield diverse Ag-specific responses as judged by analysis of mAbs. The use of DH and J segments is similar to that seen in human B cells, with an analogous pattern of N nucleotide insertion. Maturation of the response is accompanied by somatic hypermutation, which is particularly effective in the light chain transloci. These mice therefore allow the production of Ag-specific repertoires of both IgM,κ and IgM,λ Abs and should prove useful for the production of human mAbs for clinical use.

Antibody repertoires of four- and five-feature translocus mice carrying human immunoglobulin heavy chain and kappa and lambda light chain yeast artificial chromosomes

We have produced mice that carry the human Ig heavy (IgH) and both kappa and lambda light chain transloci in a background in which the endogenous IgH and kappa loci have been inactivated. The B lymphocyte population in these translocus mice is restored to about one-third of normal levels, with preferential (3:1) expression of human lambda over human kappa. Human IgM is found in the serum at levels between 50 and 400 microg/ml and is elevated following immunization. This primary human Ab repertoire is sufficient to yield diverse Ag-specific responses as judged by analysis of mAbs. The use of DH and J segments is similar to that seen in human B cells, with an analogous pattern of N nucleotide insertion. Maturation of the response is accompanied by somatic hypermutation, which is particularly effective in the light chain transloci. These mice therefore allow the production of Ag-specific repertoires of both IgM,kappa and IgM,lambda Abs and should prove useful for the production of human mAbs for clinical use.

B-cell tumorigenesis in mice carrying a yeast artificial chromosome-based immunoglobulin heavy/c-myc translocus is independent of the heavy chain intron enhancer (Emu)

We have used YAC (yeast artificial chromosome) technology to create large translocation regions where the c-myc proto-oncogene is coupled to the core region of the human immunoglobulin heavy chain (IgH) locus (from VH2-5 through to Cdelta). Chimeric mice were obtained from embryonic stem cells carrying a single copy of the 240-kb IgH/c-myc translocation region. B-cell tumorigenesis occurs in the translocus mice, even when the entire Emu intron enhancer region between the joining segments and switch mu is deleted. This demonstrates that as yet unidentified regulatory elements in the IgH locus, independent from the known enhancers, are sufficient to cause B-cell specific activation of c-myc after translocation. The phenotype of tumors from IgH/c-myc YAC transgenic mice with or without Emu (B220+, IgM+/IgD+) is reminiscent of Burkitt's lymphoma. A rapidly expanding abnormal B-cell population is present at birth and accumulates in bone marrow, periphery, and spleen, well before discrete tumor establishment. Molecular analysis identified a clonal origin, with rearrangement of one mouse heavy chain allele retained in tumor cells from different sites, whereas subsequent rearrangements of heavy or light chain loci can be diverse. These mice routinely develop mature B-cell tumors early in life and may provide an invaluable resource of a B-cell lymphoma model.

A human immunoglobulin lambda locus is similarly well expressed in mice and humans

Transgenic mice carrying a 380-kb region of the human immunoglobulin (Ig) lambda light (L) chain locus in germline configuration were created. The introduced translocus on a yeast artificial chromosome (YAC) accommodates the most proximal Iglambda variable region (V) gene cluster, including 15 Vlambda genes that contribute to >60% of lambda L chains in humans, all Jlambda-Clambda segments, and the 3' enhancer. HuIglambdaYAC mice were bred with animals in which mouse Igkappa production was silenced by gene targeting. In the kappa-/- background, human Iglambda was expressed by approximately 84% of splenic B cells. A striking result was that human Iglambda was also produced at high levels in mice with normal kappa locus. Analysis of bone marrow cells showed that human Iglambda and mouse Igkappa were expressed at similar levels throughout B cell development, suggesting that the Iglambda translocus and the endogenous kappa locus rearrange independently and with equal efficiency at the same developmental stage. This is further supported by the finding that in hybridomas expressing human Iglambda the endogenous L chain loci were in germline configuration. The presence of somatic hypermutation in the human Vlambda genes indicated that the Iglambda-expressing cells function normally. The finding that human lambda genes can be utilized with similar efficiency in mice and humans implies that L chain expression is critically dependent on the configuration of the locus.

Construction and characterisation of a functional CD19 specific single chain Fv fragment for immunotherapy of B lineage leukaemia and lymphoma

The B cell specific antigen CD19 is a target for the immunotherapy of B lineage leukaemias and lymphomas. We have engineered a single chain Fv (scFv) fragment from the mouse hybridoma cell line FMC63 which produces monoclonal antibody specific for CD19. The genes encoding the FMC63 heavy and light chain variable regions were amplified from cDNA and a scFv was constructed by splice overlap extension PCR. Analysis of staining of lymphoblastoid cell lines, peripheral blood lymphocytes and tonsil sections demonstrated that the monovalent scFv fragment has the same cellular specificity as the parent hybridoma antibody. Kinetic studies with radiolabelled material showed that the scFv binds target cells with a Ka of 2.3 x 10(-9), compared with 4.2 x 10(-9) for the parent antibody. This CD19 scFv will be used in experimental models to test its therapeutic efficacy and immunogenicity, with a view to application in the diagnosis and treatment of human B cell cancers.

Somatic hypermutation of immunoglobulin genes in human neonates

The antibody response in the young infant is limited in several ways; in particular, responses generally are of low affinity and restricted to IgM. This raises the question whether the affinity maturation process, consisting of somatic mutation of immunoglobulin genes coupled with selection of high-affinity variants, is operative in the neonate. Re-arranged V(H)6 genes were amplified by polymerase chain reaction (PCR) from cord blood and from peripheral blood of infants. Heteroduplex analysis detected mutation in only 2/18 cord blood samples, while mutations were seen from about 10 days of age onwards. Cloning and sequencing of mutated neonatal V(H)6 genes showed that mutated sequences contained relatively few mutations (one to three mutations per sequence) compared with published values of about 10 in adult IgM sequences. Selection was not evident in the majority of neonatal samples. Thus mutation can occur in the human neonate, but is minimal and generally not accompanied by selection. The age at which affinity maturation develops effectively is yet to be defined.

Memory B lymphocytes in human tonsil do not express surface IgD

To clarify the phenotype of memory B lymphocytes, we have determined the frequency of somatic hypermutations in purified tonsil B cell populations. Our particular interest was the controversial question of whether any memory B-cells express IgD. Ig heavy chain gene rearrangements that used the nonpolymorphic VH6 gene were amplified by PCR, cloned, and sequenced. All eight sequences obtained from the surface IgD (sIgD)-negative fraction contained point mutations, with frequency of one mutation in every 24 bases of sequence. In contrast, only 4 of 12 sequences obtained from the sIgD-positive fraction contained point mutations, with a mutation frequency of one in 600. This frequency was similar to that found for cord blood B cells (one in 550), a population that does not contain memory B cells. These results indicate that although memory B cells are present in the sIgD-negative fraction, no memory cells can be detected in the sIgD-positive fraction of tonsil B lymphocytes.

Memory B lymphocytes in human tonsil do not express surface IgD

To clarify the phenotype of memory B lymphocytes, we have determined the frequency of somatic hypermutations in purified tonsil B cell populations. Our particular interest was the controversial question of whether any memory B-cells express IgD. Ig heavy chain gene rearrangements that used the nonpolymorphic VH6 gene were amplified by PCR, cloned, and sequenced. All eight sequences obtained from the surface IgD (sIgD)-negative fraction contained point mutations, with frequency of one mutation in every 24 bases of sequence. In contrast, only 4 of 12 sequences obtained from the sIgD-positive fraction contained point mutations, with a mutation frequency of one in 600. This frequency was similar to that found for cord blood B cells (one in 550), a population that does not contain memory B cells. These results indicate that although memory B cells are present in the sIgD-negative fraction, no memory cells can be detected in the sIgD-positive fraction of tonsil B lymphocytes.

Rapid detection of immunoglobulin gene somatic hypermutation using heteroduplex formation

In order to identify somatic hypermutation of rearranged human immunoglobulin genes, we have examined heteroduplex formation between cloned VH6 genes. In test systems, the presence of five or more point mutations could be detected by examining the formation of heteroduplexes between a known germline VH6 gene and other sequenced genes using polyacrylamide gel electrophoresis. If a mutated sequence was used, then the presence of two or more mutations could be detected. The method was used for rapid screening of VH6-D-JH rearrangements for the presence of point mutations before sequencing, and to distinguish between different highly mutated sequences, allowing clones containing the same rearrangement to be identified indirectly.