Molecular evolution of the human immunoglobulin E response: high incidence of shared mutations and clonal relatedness among epsilon VH5 transcripts from three unrelated patients with atopic dermatitis.

We have analyzed the nucleotide sequences of 19 epsilon VH5 transcripts derived from in vivo isotype switched peripheral blood B cells of three patients with atopic dermatitis. Comparison with the patients' own germline VH5 gene segments revealed that the epsilon transcripts were derived from both functional members of the human VH5 gene family and harbored numerous somatic mutations (range 5-36 per VH5 gene). In two patients, we detected clonally related but diverged transcripts, permitting the construction of a genealogical tree in one patient. We observed a high proportion of shared silent (S) and replacement (R) mutations among epsilon VH5 sequences derived from all three individuals, even among transcripts descending from the two different germline VH5 gene segments. A remarkably high number of these mutations is shared with previously reported VH5 genes encoding antibodies with defined specificities. The shared S mutations, and likely a fraction of the R mutations, appear to mark preferential sites ("hot spots") of somatic hypermutations in human VH5 genes. The distribution of R and S mutations over complementarity determining region and framework regions in the majority of VH regions deviated from that characteristic of antigen-driven immune response. We hypothesize that the V regions of immunoglobulin E-bearing B cells have accumulated "selectively neutral" mutations over extended periods of clonal expansion, resulting in unusual R/S ratios. We propose that the molecular characteristics of the epsilon VH regions in atopic dermatitis may be representative of antigens that recurrently or chronically stimulate the immune system.

Somatic mutations in the variable regions of a human IgG anti-double-stranded DNA autoantibody suggest a role for antigen in the induction of systemic lupus erythematosus.

The processes that govern the generation of pathogenic anti-DNA autoantibodies in human systemic lupus erythematosus (SLE) are largely unknown. Autoantibodies may arise as a consequence of polyclonal B cell activation and/or antigen-driven B cell activation and selection. The role of these processes in humoral autoimmunity may be studied by molecular genetic analysis of immunoglobulin (Ig) variable (V) regions of antibodies that are characteristic of SLE. We have analyzed the gene elements that encode a high affinity, IgG anti-double-stranded DNA autoantibody secreted by a monoclonal Epstein-Barr virus (EBV)-transformed cell line derived from a patient with active SLE. In addition, we have identified, cloned, and sequenced the germline counterparts of the VH and VL genes expressed in this autoantibody. The comparison of both sets of gene elements shows that the autoantibody VH and VL regions harbor numerous somatic mutations characteristic of an antigen-driven immune response. The light chain expressed in this autoantibody is a somatically mutated variant of the kv325 germline gene that is frequently associated with paraproteins having autoantibody activity and with Ig molecules produced by malignant B cells that express the CD5 antigen. Furthermore, the utilized DH segment has been repeatedly found in multireactive, low affinity IgM anti-DNA autoantibodies from SLE patients and healthy individuals. These results suggest that pathogenic IgG anti-DNA autoantibodies in human SLE may arise through antigen-driven selection of somatic mutations in the gene elements that frequently encode multireactive IgM autoantibodies.

Autoantibodies encoded by the most Jh-proximal human immunoglobulin heavy chain variable region gene.

Little is known about the utilization of human Ig heavy chain variable gene segments (VH segments) in different B-lineage cell populations or in antibodies of particular specificity and function. We now demonstrate that human antibodies with Ig VH regions encoded by the most JH-proximal human VH segment (VH6) have specificities resembling those of autoantibodies present in sera of patients with systemic lupus erythematosus (e.g., anti-DNA and anticardiolipin). These specificities appear to be encoded by the germline VH6 gene because the activity was found in multiple independent VH6 antibodies in which the light chain varied with respect to isotype and V kappa subgroup. Features of CDR3 length and somatic mutation patterns in several VH6 antibodies suggested that they were selected by the immune system.

Synergy between tumor suppressor APC and the beta-catenin-Tcf4 target Tcf1.

Mutations in APC or beta-catenin inappropriately activate the transcription factor Tcf4, thereby transforming intestinal epithelial cells. Here it is shown that one of the target genes of Tcf4 in epithelial cells is Tcf1. The most abundant Tcf1 isoforms lack a beta-catenin interaction domain. Tcf1(-/-) mice develop adenomas in the gut and mammary glands. Introduction of a mutant APC allele into these mice substantially increases the number of these adenomas. Tcf1 may act as a feedback repressor of beta-catenin-Tcf4 target genes and thus may cooperate with APC to suppress malignant transformation of epithelial cells.

How unique are pathogenic anti-DNA autoantibody V regions?

Unique characteristics of the molecular structure of V regions encoding pathogenic anti-DNA autoantibodies have become apparent upon comparison of a large number of nucleotide sequences encoding this autospecificity. Moreover, the generation of transgenic animals expressing V regions encoding anti-DNA autoantibodies has shed light on the tolerizing mechanisms that regulate B cells producing antibodies against DNA.

A recombinant, fully human monoclonal antibody with antitumor activity constructed from phage-displayed antibody fragments.

A single-chain Fv antibody fragment specific for the tumor-associated Ep-CAM molecule was isolated from a semisynthetic phage display library and converted into an intact, fully human IgG1 monoclonal antibody (huMab). The purified huMab had an affinity of 5 nM and effectively mediated tumor cell killing in in vitro and in vivo assays. These experiments show that nonimmunized phage antibody display libraries can be used to obtain high-affinity, functional, and clinically applicable huMabs directed against a tumor-associated antigen.

Antitumor immune effector mechanisms recruited by phage display-derived fully human IgG1 and IgA1 monoclonal antibodies.

We have constructed a recombinant, fully human IgA1 monoclonal antibody, UBS-54/IgA1, against the tumor-associated Ep-CAM molecule and compared its tumor-killing capacity with its IgG1 counterpart in in vitro assays. The data show that phage display-derived fully human IgA1 antibodies efficiently recruit immune effector cells that express the Fc receptor for IgA, FcalphaRI (CD89). UBS-54/IgA1-mediated killing of tumor cells by isolated polymorphonuclear cells (PMNs) and in whole blood was found to proceed without the necessity to preactivate effector cells with cytokines. In addition, the IgA1 anti-Ep-CAM human monoclonal antibody (huMab) triggered phagocytosis of tumor cells by monocyte-derived macrophages. Strikingly, simultaneous addition of IgA1 and IgG1 anti-Ep-CAM antibodies did not result in enhancement of tumor cell killing unless the effector cells were stimulated with granulocyte colony-stimulating factor. The lack of an additive effect could be attributed to an inhibitory effect of IgG on IgA-mediated tumor cell killing through binding of IgG1 to the inhibitory FcgammaRIIb receptor expressed by PMNs. These results show that IgA1 antitumor huMabs are capable of recruiting the large population of peripheral blood PMNs for tumor cell killing. This population is not effectively recruited by IgG type antibodies, currently the antibodies most frequently used for clinical application. In addition, the data suggest that a combination of IgG1 and IgA1 antitumor huMabs may collaborate in tumor cell killing in patients treated with granulocyte colony-stimulating factor.

Selection and application of human single chain Fv antibody fragments from a semi-synthetic phage antibody display library with designed CDR3 regions.

We have constructed a large (3.6 x 10(8) clones) phage display library of human single chain Fv (scFv) antibody fragments by combining 49 germline VH genes with synthetic heavy chain CDR3 (HCDR3) regions and seven light chains. The HCDR3 regions varied in length between 6 and 15 residues and were designed to contain fully randomized stretches of amino acid residues flanked by regions of limited residue variability that were composed of amino acid residues that frequently occur in natural antibodies. We reasoned that this approach would increase the frequency of functional molecules in our library and, in addition, permit us to efficiently utilize available cloning space. By direct selection on solid phase-bound antigens we obtained phage antibodies with binding activities to 13 different antigens, including Von Willebrand factor, the DNA-binding HMG box of transcription factor TCF-1 and the tumor antigen EGP-2. In addition, we applied a competitive selection procedure to target phage antibodies to the desired portion of a recombinant fusion protein and to select phage antibodies capable of discriminating between the two highly homologous homeobox proteins PBX1a and PBX2. The functional capacity of monoclonal phage antibodies was assessed in immuno-histochemical staining of tissue specimens. Western blotting assays and immunofluorescent analysis of cells by flow cytometry. The results demonstrate that this large human phage antibody library contains a broad assortment of binding specificities that can be applied in a variety of biochemical assays.

Monitoring of neutrophil priming in whole blood by antibodies isolated from a synthetic phage antibody library.

Neutrophil activation is a multistep process. In vitro activation of neutrophils with semiphysiological activators is optimal only after preactivation or priming with cytokines, chemotaxins, and/or bacterial products. Until now, no antibodies have been developed that can distinguish between resting and (cytokine) primed neutrophils with a sufficient dynamic range necessary for screening clinical samples. We have isolated two human phage antibodies, designated MoPhab A17 and A27, from a synthetic bacteriophage antibody library. These phage antibodies recognize epitopes that are upregulated on neutrophils present in whole blood treated with low priming concentrations of cytokines, such as GM-CSF and TNF-alpha. This induction was time- and concentration-dependent and optimal at concentrations that are sufficient for priming functional responses in neutrophils: GM-CSF (10 pM) and TNF-alpha (100 IU/ml). PMNs, isolated from the peripheral blood of chronic obstructive pulmonary disease (COPD) patients with a clinical exacerbation, exhibited a partial in vivo primed phenotype. These antibodies promise to be an ideal tool to monitor disease activity in whole blood of patients with inflammatory diseases.

Biosynthetically lipid-modified human scFv fragments from phage display libraries as targeting molecules for immunoliposomes.

A human anti-CD22 single chain (sc) Fv antibody fragment from a synthetic phage antibody display library was biosynthetically lipid-tagged by using Escherichia coli lipoprotein sequences. The purified anti-CD22 scFv lipoprotein was incorporated into liposomes by detergent dilution. Anti-CD22 immunoliposomes were shown to bind specifically in a dose- and time-dependent manner to CD22+ cell lines and CD22+ B-lymphocytes present in freshly isolated samples of blood mononuclear cells. The immunoliposomes were demonstrated to accumulate in intracellular compartments. Biosynthetically lipid-tagged human scFv antibody fragments isolated from phage display libraries may facilitate the construction of immunoliposomes with improved properties.

Sural nerve T-cell receptor Vbeta gene utilization in chronic inflammatory demyelinating polyneuropathy and vasculitic neuropathy.

OBJECTIVE: To investigate the utilization of T-cell receptor (TCR) variable (V) regions in infiltrates of sural nerve biopsies of patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and vasculitic neuropathy. BACKGROUND: The presence of infiltrating T lymphocytes in sural nerve biopsies may suggest a T cell-mediated immune mechanism in the pathogenesis of CIDP and vasculitic neuropathy. PATIENTS AND METHODS: The utilization of TCR Vbeta regions in sural nerves of 13 patients with CIDP and five patients with vasculitic neuropathy was determined by immunohistochemistry, reverse-transcription PCR, and nucleotide sequence analysis. These techniques were also applied in four patients with chronic idiopathic axonal polyneuropathy (CIAP) who acted as noninflammatory controls, and in five autopsy controls. RESULTS: The TCR Vbeta utilization of infiltrating T cells in sural nerves of patients with CIDP, vasculitic neuropathy, and noninflammatory controls is heterogeneous. A dominant TCR Vbeta utilization was not found in any of the patients or controls. CONCLUSION: There is no evidence for the presence of clonally expanded T cells in sural nerves of patients with CIDP and vasculitic neuropathy.

The diagnostic value of sural nerve T cells in chronic inflammatory demyelinating polyneuropathy.

BACKGROUND: T-cell infiltrates in sural nerve biopsy specimens of patients with inflammatory neuropathies have been reported, suggesting a role for T cells in the pathogenesis, but the specificity of the presence and localization of sural nerve T cells in chronic inflammatory demyelinating polyneuropathy (CIDP) is unknown. OBJECTIVE: To study the diagnostic value of the number and distribution of sural nerve T cells in CIDP. METHODS: We performed a quantitative immunohistochemical examination of T cells in sural nerve biopsy specimens taken from 23 patients with a CIDP and compared them with sural nerves of 15 patients with a chronic idiopathic axonal polyneuropathy (CIAP), 5 patients with a vasculitic neuropathy, and 10 normal controls. RESULTS: T cells were found in sural nerves of all CIDP patients as well as in all disease and normal controls. Only six CIDP patients had increased numbers and densities of T cells compared with CIAP patients and controls. Based on the distribution of endoneurial or epineurial T cells, it was not possible to differentiate CIDP patients from CIAP patients or normal controls. In patients and controls perivascular epineurial T cells predominated. Increased numbers and densities of sural nerve T cells in patients with CIDP were associated with female sex, a more severe disease course, worse outcome, highly elevated CSF protein level, and a larger sural nerve area, but not with loss of myelinated nerve fibers in the sural nerve biopsy sample or demyelinating features on electrophysiologic examination. CONCLUSIONS: In the majority of CIDP patients, the number and distribution of T cells in sural nerve biopsy samples were similar to patients with noninflammatory neuropathies and normal controls. Only large numbers of sural nerve T cells are specific for inflammatory neuropathies and therefore of diagnostic value for CIDP.

Phage antibodies against human dendritic cell subpopulations obtained by flow cytometry-based selection on freshly isolated cells.

In one application of phage display technology, large libraries of antibody fragments displayed on phage particles are used to select antibodies that bind to molecules expressed on the surface of eukaryotic cells. The advantage of this method is that antibodies can be selected against antigens in their native configuration, without the need to purify or express the antigen as a recombinant protein. Moreover, this approach may be used to search for novel membrane molecules expressed by subpopulations of cells that are difficult to address by conventional methods, e.g., small numbers of cells present in heterogeneous mixtures. It has been shown that the isolation of cell-bound phages is compatible with immunofluorescence staining and flow cytometric identification and sorting of cells based on multiparameter analysis. Here, we have employed a semi-synthetic phage display library of human single-chain Fv (scFv) antibody fragments in combination with flow cytometry to isolate antibodies against rare populations of precursor and mature dendritic cells (DCs) present in human peripheral blood. DCs are a phenotypically heterogeneous population of professional antigen presenting cells of bone marrow origin with complex and only partly understood developmental relationships and functions. We have isolated phage antibodies against subpopulations of blood DCs and analyzed the distribution of the target antigens. The results show that these phage antibodies are useful tools to further dissect relationships and function of DCs in healthy and diseased tissues.

Enumeration of IFN-gamma-producing human lymphocytes by spot-ELISA. A method to detect lymphokine-producing lymphocytes at the single-cell level.

We present a method to detect and enumerate individual interferon (IFN)-producing human lymphocytes. The assay is based on the ELISA-plaque assay developed by Sedgwick and Holt (J. Exp. Med. (1983) 157, 2178; J. Immunol. Methods (1986) 87, 37). Mitogen-stimulated T cells are seeded in anti-IFN-gamma-coated wells. After a 16 h incubation period, the cells are removed. Subsequently a rabbit anti-IFN-gamma-antiserum followed by goat anti-rabbit antiserum conjugated to alkaline phosphatase are used to detect the IFN-gamma spots. Application of the spot-ELISA in combination with the conventional ELISA reveals the amount of IFN-gamma produced per cell. The spot-ELISA is a highly sensitive, easy to perform and rapid assay. Provided specific antisera are available, this method is suitable to detect production of other lymphokines at the single-cell level. To our knowledge, this is the first report of a single, well-defined T cell product measurement by the spot-ELISA.

Functional human monoclonal antibodies of all isotypes constructed from phage display library-derived single-chain Fv antibody fragments.

We have constructed a series of eukaryotic expression vectors that permit the rapid conversion of single chain (sc) Fv antibody fragments, derived from semi-synthetic phage display libraries, into intact fully human monoclonal antibodies (mAb) of each isotype. As a model, a scFv fragment specific for sheep red blood cells (SRBC) was isolated from a semi-synthetic phage antibody (Ab) display library, and used to produce human mAbs of IgM, IgG1-IgG4, IgA1, IgA2m(1) and IgE isotype in vitro in stably transfected cells. N-terminal protein sequence analysis of purified immunoglobulin heavy (H) and light (L) chains revealed precise proteolytic removal of the leader peptide. Biochemical analysis of purified recombinant human mAbs demonstrated that properly glycosylated molecules of the correct molecular size were produced. The IgG and IgA mAbs retained SRBC-binding activity, interacted with different Fc receptor-transfectants, and induced complement-mediated hemolysis and Ab-dependent phagocytosis of SRBC by neutrophils in a pattern consistent with the immunoglobulin (Ig) H chain isotype. We conclude that in vitro produced recombinant human mAbs constructed from phage display library-derived scFv fragments mirror their natural counterparts and may represent a source of mAbs for use in human therapy.

Increased frequencies of HPRT mutant T lymphocytes in patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy: further evidence for a role of T cells in the etiopathogenesis of peripheral demyelinating diseases.

We have used the HPRT mutant clonal assay to determine the frequency of mutant T lymphocytes (FMC), as a measure of recent T cell stimulation, in the blood of patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP). We found that, compared to healthy controls, the FMC in patients with GBS (16) and CIDP (10) was significantly increased in the progressive phase of the neuropathy. FMC returned to normal values during recovery, suggesting a relationship between FMC and disease activity. No correlation was found between FMC values and motor deficit or severity of the neuropathy. The FMC of the GBS patients with a history of infection before onset of neurological symptoms or with insufficient respiration was not significantly different from the other GBS patients. Immunophenotypic analysis showed that the fraction of CD8+ HPRT mutant T cell clones was significantly increased in GBS patients (48%) compared to healthy controls (3%) or CIDP patients (4.5%). Our results are compatible with the notion that T cells are involved in the pathogenesis of demyelinating inflammatory neuropathies.

Enumeration of (auto)antibody producing cells in human using the "spot-ELISA".

An enzyme-linked immunosorbent assay (spot-ELISA) for individual immunoglobulin secreting cells, which became recently available, was applied to the enumeration of human B lymphocytes secreting specific antibodies of thyroglobulin. Polyclonally activated B cells from patients with auto-immune thyroid disease are incubated in thyroglobulin coated plates. After removal of the cells specific antibodies are visualized by means of an immunoenzyme technique employing agarose to localize converted substrate. Individual specific antibody secreting cells are counted as blue spots using an inverted microscope. Numbers and isotype of spots correlate well with the amount and isotype of secreted antibody as detected with a conventional ELISA. This easy to perform, complement-independent technique offers a useful alternative to conventional plaque forming cell assays.

Generation of the (auto)-antibody repertoire: a case of narcissism?

The immune system has the tremendous task of recognizing and eliminating a practically unlimited number of foreign and often harmful substances. To reach that goal, it has evolved as an apparatus generating a vast array of different antigen receptors expressed by T and B lymphocytes. Through these receptors, the cells can recognize, and respond to, foreign structures; nevertheless, the lymphocytes do not normally react to the body's own constituents. The processes that safeguard a sufficiently broad diversity and yet prevent potentially pathogenic autoimmune reactivity are only now beginning to be elucidated. We describe some of the mechanisms that are believed to play a major role in the generation of the B lymphocyte and antibody repertoire, the induction of tolerance against autologous components and the production of pathogenic autoantibodies, once tolerance is broken.

Peanut agglutinin (PNA) binding as a marker for immature human B lymphocytes. Is bone marrow not the complete bursa-equivalent?

To investigate the nature of peanut agglutinin (PNA) binding cells in various human lymphoid tissues a double marker assay was performed using fluorescent PNA and rosetting with anti-mu or anti-delta coated ox red blood cells for detection of B cells or rosetting with sheep red blood cells for detection of T cells. In human bone marrow 60.5 +/- 8.6% of the surface mu+ve (smu+ve) B cells did bind PNA whereas only a small minority of the surface delta +ve (delta +ve) B cells (5.0 +/- 4.2%) and none of the T cells were PNA+ve. In peripheral blood most of the PNA+ve cells appeared to be monocytes. Only a small proportion of the smu+ve B cells (9.7 +/- 2.7%) and none of the s delta +ve B cells or T cells did bind PNA. Contrarily in tonsils a relatively high proportion of smu+ve B cells (33.2%) of s delta +ve B cells (26.3%) and of T cells (17.2%) were PNA+ve. These results indicate that PNA binding is also a marker for immature B cells. Moreover in human bone marrow at least two populations of B cells may be distinguished, an immature population of smu+ve, s delta-ve, PNA+ve B cells and a mature populations of smu+ve, s delta +ve, PNA-ve B cells, the latter probably representing recirculating B cells. We hypothesize that the first population comprises immature B cells, that leave the bone marrow in an early stage and complete the maturation to immunocompetent B cells in peripheral lymphoid organs like tonsils.