Generation and molecular analyses of two rheumatoid synovial fluid-derived IgG rheumatoid factors

OBJECTIVE

To study the Ig genes that encode IgG rheumatoid factor (IgG-RF) from rheumatoid synovial fluid.

METHODS

We used rheumatoid synovial fluid B cells to generate IgG-RF-secreting hybridomas. We then characterized their binding properties and determined their nucleotide sequences.

RESULTS

Two monospecific IgG-RFs were obtained. Sequence analysis of the RFs revealed a new V lambda gene family (designated V lambda 9) and extensive somatic diversification, including a duplication-insertion of 18 nucleotides (6 amino acid residues) into a hypervariable region.

CONCLUSION

The data provide further support for an antigen-driven response in the sustained production of potentially pathogenic IgG-RFs in rheumatoid synovium.

Apoptosis and disease

The intercellular connections that characterise advanced forms of life would not be possible without a mechanism to remove individual cells that are no longer needed, or that function abnormally. Such physiological cell death, in the absence of inflammation, is achieved by apoptosis, a structurally distinct programmed cell death pathway. Defective regulation of programmed cell death may play a part in the aetiology of cancer, AIDS, autoimmune diseases, and degenerative diseases of the central nervous system. The pharmacological manipulation of apoptosis offers new possibilities for the prevention and treatment of these illnesses.

Systemic immunological effects of cytokine genes injected into skeletal muscle

Somatic gene therapy is an interesting approach for the delivery of cytokines for prolonged periods. The present experiments show that direct injections into mouse skeletal muscle of cDNA expression vectors encoding interleukin 2 (IL-2), IL-4, or type beta 1 transforming growth factor (TGF-beta 1) induce biological effects characteristic of these cytokines in vivo. Mice injected intramuscularly with a vector encoding IL-2 had enhanced humoral and cellular immune responses to an exogenous antigen, transferrin, that was delivered at a separate site. These IL-2 effects were abolished by coadministration of a vector directing synthesis of TGF-beta 1. The TGF-beta 1 vector by itself depressed the anti-transferrin antibody response and caused an 8-fold increase in plasma TGF-beta 1 activity. The TGF-beta 1 plasmid injection did not cause muscle infiltration with monocytes or neutrophils and there was no evidence for fibrotic changes. Muscle injection with a cDNA encoding IL-4 selectively increased IgG1 levels but did not alter the cellular immune response to transferrin. In lupus-prone mice (MRL/lpr/lpr), injection with IL-2 expression vectors increased and TGF-beta 1 vectors decreased auto-antibodies to chromatin. These results demonstrate that intramuscular injection of cytokine genes, in the absence of infectious viral vectors, can regulate humoral and cellular immune responses in vivo.

Transforming growth factor-beta (TGF beta) inhibition of Epstein-Barr virus (EBV)- and interleukin-4 (IL-4)-induced immunoglobulin production in human B lymphocytes

This study reports on the effects of TGF beta on the secretion of Ig isotypes by highly purified (> 99% CD20-positive) human peripheral blood B cells. Stimulation of these B cell preparations with EBV resulted in the secretion of IgM, IgG, and IgA and the addition of IL-4 induced readily detectable levels (> 100 ng/ml) of IgE between 10 and 25 days of culture. TGF beta 1 and TGF beta 2 showed similar dose-dependent suppression of IgM, IgG, and IgA, and the relative proportion of IgG and IgA remained unchanged in the presence of TGF beta. IgE production induced by EBV and IL-4 was significantly inhibited by TGF beta. TGF beta effects on Ig secretion were not related to inhibition of B cell proliferation by this cytokine. In contrast to these TGF beta effects on EBV activation of primary B cells, the constitutive Ig secretion by EBV-transformed B cells was resistant to TGF beta, while the increase in Ig secretion induced by IL-6 was inhibited by TGF beta. Thus, TGF beta inhibits the EBV-induced secretion of the major Ig isotypes in peripheral blood B cells and has differential effects on Ig secretion by transformed B cells.

2-Chlorodeoxyadenosine dose escalation in nonhematologic malignancies

PURPOSE

We performed a dose-escalation study of 2-chlorodeoxyadenosine (2-CdA) in solid tumors to determine the maximum-tolerated dose (MTD) and define its toxicity profile at higher doses.

PATIENTS AND METHODS

Twenty-one patients, seven with malignant astrocytoma, twelve with metastatic melanoma, and two with metastatic hypernephroma, were enrolled onto the study. Patients were entered onto cohorts that received 0.10, 0.15, or 0.20 mg/kg/d of 2-CdA by continuous intravenous infusion for 7 days every 28 days. 2-CdA levels were determined by radioimmunoassay. In tumor tissue samples, deoxycytidine kinase (dCK) levels were measured by both enzyme activity and immunoreactive protein analysis.

RESULTS

Of seven patients treated with 2-CdA at 0.1 mg/kg/d, one experienced grade 3 or 4 myelotoxicity. Of 11 patients treated at 0.15 mg/kg/d, four experienced myelotoxicity, two after a single course of 2-CdA. All three patients who received 2-CdA at 0.2 mg/kg/d experienced myelosuppression. Neurologic events occurred in two patients, both with malignant melanoma. Two of seven patients (28.6%) with astrocytomas obtained partial responses with a median duration of 8 months. 2-CdA penetrated the blood-brain barrier. An association was found between dCK levels as measured by enzymatic activity and immunoreactive proteins, but this did not correlate with 2-CdA tumor responsiveness.

CONCLUSION

The MTD for 2-CdA delivered as a 7-day intravenous infusion in patients with nonhematologic malignancies was determined to be 0.1 mg/kg/d, the same as the MTD for patients with hematologic malignancies. There was no clinical correlation with dCK expression and response to 2-CdA. The responses noted in patients with malignant astrocytoma warrant further phase II study.

Characterization of two highly homologous autoantibody-related VH1 genes in humans

Previously, we showed that the Humha 1lr rearranged gene was almost identical to the consensus amino acid sequence of several G6 idiotype-positive rheumatoid factor (RF) heavy chains, and to the VH gene-encoded region of the fetally expressed 51P1 cDNA. The finding led us to suggest that the ha 1lr-corresponding germline gene encodes the heavy chains of many human IgM RFs. We now report the isolation of the proposed germline gene, designated Humhv1051; it is identical to the consensus sequence of the G6 heavy chain V regions. During this experiment, we also isolated unexpectedly an additional VH1 gene, termed Humhv1051K; it differs from hv1051 by one amino acid residue. Importantly, hv1051K is identical to Humha113, the rearranged VH1 gene of a natural anti-cardiolipin antibody.

Methylthioadenosine phosphorylase deficiency in human non-small cell lung cancers

Methylthioadenosine (MeSAdo) phosphorylase, a purine metabolic enzyme, is present in all normal mammalian tissues. A deficiency of this enzyme has been reported in some human leukemias and lymphomas and in a few solid tumors. In the present study, a specific immunoassay was used to assess the enzyme levels in human non-small cell lung cancer cell lines and primary tumors. We also tested the effects of MeSAdo phosphorylase-selective chemotherapy on the in vitro growth of enzyme-positive and enzyme-negative lung cancer cell lines. Of 29 non-small cell lung cancers, 9 (6 cell lines and 3 primary tumors, 31%) lacked detectable immunoreactive enzyme protein. Both 5,10-dideazatetrahydrofolate, an inhibitor of de novo purine synthesis, and methionine depletion, combined with MeSAdo, prevented the growth of the enzyme-negative non-small cell lung cancer cells under conditions in which enzyme-positive cells utilized MeSAdo to endogenously synthesize purine nucleotides and methionine. Our data suggest that MeSAdo phosphorylase deficiency is frequently found in non-small cell lung cancers and can be exploited in designing enzyme-selective chemotherapy.

Divergent T cell receptor gamma repertoires in rheumatoid arthritis monozygotic twins

OBJECTIVE

To determine if the expressed T cell receptor (TCR) gamma repertoire is altered in rheumatoid arthritis (RA).

METHODS

Peripheral blood lymphocytes were collected from monozygotic twins who were either concordant or discordant for RA, or from a normal twin pair. TCR gamma-specific complementary DNA libraries were constructed using the anchored polymerase chain reaction. Gene usage was analyzed by plaque hybridization and sequencing.

RESULTS

The expressed TCR V gamma repertoires both in RA patients and normal subjects were extremely diverse. Monozygotic twins who were concordant for RA expressed very different frequencies of TCR V gamma genes.

CONCLUSION

RA does not lead to a specific clonal expansion or deletion of TCR V gamma genes in peripheral blood.

Relationship of deoxycytidine kinase and cytoplasmic 5'-nucleotidase to the chemotherapeutic efficacy of 2-chlorodeoxyadenosine

The agent 2-chlorodeoxyadenosine (2-CdA) has chemotherapeutic activity in hairy cell leukemia (HCL) and in refractory chronic lymphocytic leukemia (CLL). The cytotoxic activity of 2-CdA requires the intracellular accumulation of 2-CdA nucleotides. Deoxycytidine kinase (dCK) and cytoplasmic 5'-nucleotidase (5'-NT) are the principal enzymes that phosphorylate 2-CdA and dephosphorylate 2-CdA 5'-monophosphate, respectively. The net accumulation of 2-CdA nucleotides may therefore depend on both dCK and 5'-NT. The purpose of the present experiments was to determine if there is a relationship between pretreatment levels of dCK and 5'-NT in HCL and in CLL cells, and the clinical outcome of 2-CdA treatment. As measured by a direct immunoassay for dCK in 25 CLL patients, and by a 5'-NT activity assay in 23 patients, mean dCK levels were significantly higher in 2-CdA responders than in nonresponders (P < .01), whereas mean 5'-NT levels were significantly lower in 2-CdA responders than in nonresponders (P < .05). Mean dCK levels were higher in six HCL 2-CdA responders than in one nonresponder, whereas mean 5'-NT levels were lower in the 2-CdA responders than in the nonresponder. These results suggest that both dCK and 5'-NT are determinants of 2-CdA responsiveness.

Function of B cells expressing a human immunoglobulin M rheumatoid factor autoantibody in transgenic mice

We have generated transgenic mice that express the immunoglobulin (Ig)M heavy chain and kappa light chain genes coding for a human IgM rheumatoid factor (RF), Les. Transgenic B cells expressing human IgM RF show striking similarities to their counterparts in normal humans. They comprise a significant proportion of the adult B cell population, but secrete only low levels of RF into the serum. The RF transgene-expressing B cells localize to primary B cell follicles and the mantle zone regions of secondary follicles in the spleen. Using these mice we have been able to show that one of the central functions of normal RF-expressing B cells may be to act as highly efficient antigen-presenting cells for low concentrations of immune-complexed antigen. High levels of secretion of IgM RF can not be induced under normal circumstances, although RF-expressing B cells proliferate well in vitro to both aggregated human IgG and anti-human IgM antibodies. However, these mice are not intrinsically secretion deficient. By crossing the RF transgenic mice with the autoimmune MRL/lpr background, we find a dramatic increase, > 200-fold, in levels of serum RF. The results strongly suggest that a major function of normal resting RF B cells is unrelated to antibody secretion. Rather, the RF B cells in the follicles may play a role in antigen presentation and regulation of immune responses to antibody-bound nonself-, and possibly self-antigens. This physiologic role of RF B cells may be disrupted in RF-associated autoimmune disease.

Regulation of the mature human T cell receptor gamma repertoire by biased V-J gene rearrangement

To delineate how gene rearrangement influences the expressed human gamma delta T cell repertoire, we generated T cell receptor gamma (TCR gamma) V domain-specific cDNA libraries from the peripheral lymphocytes of eight donors and sequenced a total of 232 TCR gamma gene transcripts. The libraries consisted of both in-frame and out-of-frame rearranged TCR gamma genes. The in-frame TCR gamma gene transcripts were used to determine the diversity of functional T cells, whereas the out-of-frame transcripts, primarily derived from alpha beta T cells, were used to assess the frequencies of TCR V gamma-J gamma rearrangements in progenitor T lymphocytes. The results showed that both sets of transcripts exhibited strikingly restricted V gamma-J gamma combinations. Only 11 of 40 potential V gamma-J gamma rearrangements were common ( > or = 3% of total). The pattern of gene usage in the functional and nonfunctional transcripts was similar and did not differ markedly among donors. The only exception was the predominance of V gamma 9-JP in potentially functional transcripts from seven of eight individuals. These results show that V gamma-J gamma rearrangement is nonrandom and suggest that the diversity of TCR gamma genes in the functional gamma delta T cell repertoire partly depends upon preferentially rearranged V gamma-J gamma gene combinations. However, the expansion of V gamma 9/V gamma 2 T cells in adult peripheral blood can only be explained by antigenic selection of relatively rare V gamma 9-JP recombinants.

Sequence analyses of three immunoglobulin G anti-virus antibodies reveal their utilization of autoantibody-related immunoglobulin Vh genes, but not V lambda genes

Accumulated sequence analyses of the antibody repertoire have revealed that most autoantibodies and developmentally regulated antibodies share a small set of germline Ig-variable region (V) genes. The findings have prompted speculation that certain autoantibodies are of developmental importance and may be instrumental in maintaining homeostasis of the adult antibody repertoire. In order to evaluate this hypothesis critically, it is first necessary to determine the V gene usage in human antibodies against foreign substances. Unfortunately, only a few such antibodies have had their heavy and light chains characterized. To rectify the situation, we adapted the anchored polymerase chain reaction to clone and analyze rapidly the expressed V genes for three anti-virus IgG antibodies. The results show that all three heavy chain V (Vh) genes are highly homologous to the known autoantibody-related Vh genes. In contrast, two light chain V (VL) genes of the V lambda 1 subgroup are similar to a non-autoantibody-related germline V lambda 1 gene. Taken together with the reported Vh and VL sequences of several antibodies against viruses and bacteria, the data show that many antipathogen antibodies may use the same small set of Vh genes that encode autoantibodies, but diverse VL genes that are distinct from autoantibody-related VL genes. Thus, only a small portion of the potentially functional germline Vh genes are used recurrently to generate most antibodies in a normal antibody repertoire, regardless of their reactivities with either self or non-self.

Quantitative immunoassay of human deoxycytidine kinase in malignant cells

Deoxycytidine kinase (dCK) is necessary for the activity of several nucleosides used for the chemotherapy of cancer and AIDS. However, the measurement of dCK catalytic activity in crude cell extracts may be imprecise, due to the presence of phosphatases and nucleotidases that degrade the enzyme products. We describe a simple immunoassay for dCK that can measure accurately as little as 5 ng enzyme protein in crude tissue extracts. The assay enabled us to show (i) that mutant cells deficient in dCK activity lack immunoreactive dCK protein, (ii) that dCK catalytic activity and immunoreactivity correlate closely in human tumors, and (iii) that immunoreactive dCK is particularly high in lymphocytes and lymphoid malignancies, although certain solid tumors may also contain the enzyme. The immunoassay of dCK could prove useful in the selection and monitoring of patients who are being treated with nucleosides that are activated by this enzyme.

Genetic and environmental factors in the immune pathogenesis of rheumatoid arthritis

Our experiments have led us to conclude that the rheumatoid arthritis shared epitope may act as a peptide that is important for positive and negative selection of T lymphocytes, that T lymphocytes are skewed by positive selection to recognize epitopes that are similar but not identical to self, and that peptide sequences that are similar to the RA-shared epitope are abundantly expressed by microorganisms that chronically infect most people. This combination of events could partly explain the association of the shared epitope with the severe forms of RA. The hypothesis cannot be tested directly, because we do not postulate that any unique population of autoreactive T cells is expanded in RA; however, the role of positive selection in molding the human T-cell repertoire to exogenous antigens can be tested by mapping T-cell antigenic determinants on the E. coli dnaJ protein or the gp110 protein of EBV in people with different HLA-DR types. Moreover, positive selection models imply that maternal antigens that cross the placenta can influence the T-cell repertoire. Thus, one might expect to find that the frequency of HLA-DR4 in the mothers of patients with RA who themselves lack the DR4 antigen, would be more frequent than predicted by chance alone. As the principles of positive selection are more precisely delineated in animal systems, it should become possible to ascertain more clearly how the shared epitope on HLA-DR molecules enhances the severity of autoimmune reactions; however, RA only occurs in humans; possibly because of the unique inability of human macrophages to replicate. Thus, only the direct analysis of patients can directly reveal the mechanisms of disease pathogenesis.

Transfer of human chronic lymphocytic leukemia to mice with severe combined immune deficiency

B chronic lymphocytic leukemia (CLL) cells were transferred into mice with severe combined immunodeficiency (SCID). Leukemia cells injected into the peritoneal cavity of these animals may survive for at least 10 weeks in vivo. In contrast, leukemia cells do not survive for long periods when injected intravenously. Despite the longevity of CLL cells injected i.p., these cells apparently do not migrate to other lymphoid tissues. Eight to sixteen weeks after receiving CLL cells, SCID mice develop human IgG autoantibodies to human red blood cells and/or high serum levels of human Ig. Soon thereafter, these animals develop lethal human B-cell tumors. In contrast to the original CLL cells, these human B-cell tumors are CD5-negative, have genomic DNA of Epstein-Barr virus (EBV), express antigens associated with latent EBV infection and have distinctive Ig gene rearrangements by Southern. We conclude that bystander B cells may generate tumors in CLL-reconstituted SCID mice that emulate the EBV-associated lymphoproliferations noted in SCID mice reconstituted with normal human PBL.

Greatly enhanced inhibition of human immunodeficiency virus type 1 replication in CEM and HT4-6C cells by 3'-deoxythymidine diphosphate dimyristoylglycerol, a lipid prodrug of 3'-deoxythymidine

3'-Deoxythymidine (3dT) is a weakly active dideoxynucleoside in human immunodeficiency virus (HIV)-infected cells because of its slow phosphorylation by cellular thymidine kinase. 3dT diphosphate dimyristoylglycerol (3dTDP-DMG), a phospholipid prodrug, was synthesized and found in vitro to be 18- to 50-fold more effective than 3dT in CEM and HT4-6C cells. In CEM cells, the selectivity index of 3dTDP-DMG was 270 versus 48 for 3dT, an increase of 5.6-fold. In thymidine kinase-deficient mutant CEM cells infected with HIV, 3dT and zidovudine (AZT) were virtually inactive but 3dTDP-DMG retained substantial activity, suggesting that its greatly increased antiviral activity is due in part to bypass of thymidine kinase. 3dTDP-DMG was 14- to 37-fold more active than 3dT in AZT-sensitive and AZT-resistant clinical isolates of HIV; no cross-resistance with AZT was noted. The results suggest that lipid prodrugs may be utilized in some cases to confer unique metabolic advantages over the corresponding free nucleoside; in the case of 3dTDP-DMG, an 18- to 50-fold increase in antiretroviral activity was observed in LAV-infected cells. The strategy would seem to be especially useful for antiviral nucleosides which are poorly phosphorylated.

A polymerase chain reaction-based method for isolation of gene-specific sequences from the interferon-alpha gene cluster

The interferon-alpha gene is a gene family of over 20 distinct genes having 80-95% homology with one another at a nucleotide level. Because of the high homology in the gene cluster, the available interferon-alpha gene probes can hybridize to multiple bands of different size on Southern blot analysis of restricted human genomic DNA. We used the polymerase chain reaction with the primers synthesized from Alu repetitive sequence and the conserved sequences of the interferon-alpha gene cluster to generate specific probes for individual interferon-alpha genes. The amplification products were subcloned into a plasmid vector and analyzed by DNA sequencing and Southern blotting of the restricted human placental DNA. One clone, which derived from interferon-alpha 14 gene, produced a single 5.2-kb band in Southern blots of the HindIII-restricted human placental DNA. This stands in contrast to the 10 bands of different size that were detected with a cDNA for the interferon-alpha I' gene. Our results indicate that a polymerase chain reaction-based method can be used to isolate gene-specific sequences from the interferon-alpha gene cluster. Since a variety of human cancers has been found to have the complete or partial deletion of the interferon-alpha gene cluster, the gene-specific probe generated by this method may aid in determining the breakpoints in the vicinity of the gene cluster.

2-Chlorodeoxyadenosine: an active agent in the treatment of cutaneous T-cell lymphoma

Cutaneous T-cell lymphomas are disfiguring malignant lymphoproliferative disorders for which standard therapy has been principally palliative. 2-Chlorodeoxyadenosine (2-CdA), a new purine analogue resistant to degradation by adenosine deaminase that has substantial activity against lymphoid neoplasms, was administered to 16 patients with cutaneous involvement by T-cell lymphoma. All patients had failed topical treatment modalities and/or systemic therapies. Fifteen patients were evaluable; one patient was not evaluable due to incomplete therapy and follow-up. The overall response rate was 47%. Three of 15 patients (20%) achieved complete responses and four of 15 patients (27%) achieved partial responses. The median duration of response was 5 months. One patient remains in unmaintained complete remission at 52+ months. Therapy was well tolerated. Myelosuppression was the principal toxicity encountered, occurring in 8 of 15 (53%) patients. 2-CdA is an effective new agent for the treatment of cutaneous T-cell lymphoma and warrants further study both as a single agent and in combination regimens.

Inheritance of monoclonal rheumatoid factor cross-reactive idiotypes in primary Sjögren's syndrome (pSS). Comparative studies of a rabbit polyclonal anti-idiotype and 17109 monoclonal anti-idiotype

A comparison of the presence of two idiotypes, one identified by a rabbit polyclonal antiidiotypic antibody, first found on a cryoprecipitable IgM chi rheumatoid factor (RF) from an SS patient (3rd SS) and the 17109 idiotype, identified by a monoclonal antibody was performed in 106 sera and eight minor salivary gland biopsies of Sjögren's syndrome (SS) patients and 125 sera from age-sex matched normal controls. Of 106 of SS patients' sera 36 had immunoglobulins positive for the 3rd SS idiotype. 17109 activity was more prevalent in SS patients positive for the polyclonal anti-idiotype 3rd SS, than those with negative idiotype (9/36 VS 2/70 chi 2 = 12.53 P less than 0.005). Cross inhibition studies, however, revealed that the polyclonal anti-idiotype binding was not inhibited by the 17109 moAb. 3rd SS and 17109 anti-idiotypes were reacted with immunoglobulins in the serum of 3.5% and 1.7% of normal human sera respectively. Immunohistologic studies demonstrated that 4/8 and 2/6 minor salivary gland biopsies had infiltrating plasma cells containing immunoglobulins bearing the 3rd SS and the 17109 idiotypes, respectively. The inheritance of both idiotypes was investigated in sera of 4 SS kindreds. In two kindreds with 3rd SS positive probands, the idiotype was detected in 3 first degree relatives of the same generation. 17109 activity was detected in the serum of a sister of the positive proband who had a high RF titer. These results suggest that the 17109 moAb recognizes a different epitope of that of the 3rd SS. The idiotypes of monoclonal RFs are not inherited and probably are produced by plasma cells infiltrating the labial minor salivary glands of SS patients.

Genetic factors in the etiology and pathogenesis of autoimmunity

Family and population studies indicate that several different genes can increase susceptibility to autoimmune diseases. Established genetic risk factors include genes encoding histocompatibility molecules, complement proteins, immunoglobulins, peptide transporter proteins, and genes controlling the production of sex hormones. Each factor may independently enhance the immunogenicity of autoantigens, either by increasing their processing and presentation by B lymphocytes and macrophages or by increasing the chance for recognition by autoreactive T and B lymphocytes. Genetic factors may also influence immune responses to infectious agents that can trigger autoimmunity. Because of the somatic generation of immune diversity, genetically identical individuals have different immune systems. The ability of genetic diagnosis to predict autoimmune disease in outbred populations cannot easily exceed the disease concordance rates in monozygotic twins, which usually are less than 50%. However, genetic diagnosis can target populations that should be monitored for serologic evidence of autoimmunity, which may precede clinical signs and symptoms. In the future, it may be possible to match different forms of immunotherapy with specific genetic defects.

Oral antilymphocyte activity and induction of apoptosis by 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine

2-Chlorodeoxyadenosine (CdA) is active in chronic lymphocytic leukemia, hairy-cell leukemia, and low-grade lymphomas. In part, this spectrum of activity may be attributable to the selective toxicity of CdA to nondividing lymphocytes and monocytes. However, CdA is unstable at acidic pH and is degraded by bacterial nucleoside phosphorylases. The present experiments demonstrate that the 2'-arabino-fluoro derivative of CdA, designated CAFdA, is also directly toxic to quiescent lymphocytes and macrophages. Unlike CdA, CAFdA was stable at pH 2 and resisted degradation by Escherichia coli nucleoside phosphorylase. Cell killing was preceded by the formation of DNA strand breaks and could be prevented by supplementation of the medium with deoxycytidine. The initial DNA damage initiated the pattern of oligonucleosomal DNA fragmentation characteristic of apoptosis. Mutant lymphoblasts, deficient in deoxycytidine kinase, with elevated cytoplasmic 5'-nucleotidase, or with expanded deoxynucleotide pools secondary to increased ribonucleotide reductase activity, were cross-resistant to both CAFdA and CdA toxicity. One-week oral treatment with CAFdA (1 mg/ml in drinking water) achieved an average plasma concentration of 0.56 microM and eliminated 90% of chronic lymphocytic leukemia cells transplanted into severe combined immunodeficiency (scid) mice. Under the same conditions, CdA was much less active. Collectively, these results suggest that CAFdA could be effective as an oral agent in indolent lymphoproliferative diseases and in autoimmune diseases where lymphocyte and monocyte depletion is desirable.

Immunoglobulin V gene expression in CD5 B-cell malignancies

Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphomas (SLL) generally are malignancies of CD5 B cells. Immunophenotypic and clinicopathologic data, however, are required to distinguish subtypes that apparently have a different cytogenesis than that of conventional CLL or SLL. In addition to expressing CD5, neoplastic cells of the latter are also distinctive in that they frequently coexpress surface immunoglobulin (Ig), bearing one or more cross-reactive idiotypes (CRIs) (e.g. 17.109, G6,) that commonly are found on monoclonal IgM autoantibodies. The frequent occurrence of such CRIs reflects both the biased rearrangement and subsequent selected expression of Ig V genes with little or no somatic mutation. IgM/L CLL, for example, frequently (8/33) harbor abortive Ig rearrangements involving Humkv325, the VK gene encoding the 17.109-CRI. Also, the VH1 gene(s) encoding the G6 CRI accounts for over 10% of all VH genes and over 60% of all the VH1 genes used in randomly selected common CLL/SLL. Furthermore, comparison with the Ig expressed by nonmalignant G6 CRI+ B cells reveals an apparent restriction in the CDR3 of IgH expressed by G6 CRI+ CLL. Coupled with the observed potential bias in antibody light chain and heavy chain pairing in B-CLL, these data suggest that the autoantibodies expressed in this disease are selected based on antigen-binding activity. Collectively, our studies indicate that nonstochastic Ig V gene rearrangement and subsequent selection may influence the Ig repertoire expressed in this common B-cell malignancy.

Evidence for somatic selection of natural autoantibodies

Natural autoantibodies are primarily immunoglobulin M (IgM) antibodies that bind to a variety of self-antigens, including self-IgG. Accounting for a large proportion of the early B cell repertoire, such polyspecific autoantibodies are speculated to contribute to the homeostasis and/or competence of the primary humoral immune system. Recent studies indicate that the leukemia cells from most patients with chronic lymphocytic leukemia (CLL) also express such IgM autoantibodies. Similarly, the leukemia cells from many CLL patients react with murine monoclonal antibodies (mAbs) specific for crossreactive idiotypes (CRIs) associated with human IgM autoantibodies. In particular, leukemic cells frequently react with G6, a mAb specific for an Ig heavy chain (H chain)-associated CRI, and/or with 17.109, a mAb that defines a kappa light chain (L chain)-associated CRI. Generated against IgM rheumatoid factor (RF) paraproteins, G6 and 17.109 each recognize a major CRI that is present in many IgM RF paraproteins. Furthermore, over 90% of the IgM paraproteins found to bear both H and L chain-associated CRIs also are found to have RF activity. Molecular characterization of these CRIs demonstrates that each is a serologic marker for expression of a highly conserved Ig V gene. As such, the frequent production of IgM polyspecific autoantibodies in CLL simply may reflect the frequent use of such highly conserved autoantibody-encoding Ig V genes with little or no somatic mutation. To test this hypothesis, we generated murine transfectomas to pair the 17.109-reactive kappa L chain of SMI, a 17.109/G6-reactive CLL population, with the Ig H chain of SMI or other G6-reactive leukemia cells or tonsillar lymphocytes. Cotransfection of vectors encoding the Ig H and L chains of SMI generated transfectomas that produce IgM kappa RF autoantibodies reactive with human IgG1 and IgG4. In contrast to G6/17.109-reactive IgM kappa RF Waldenstrom's paraproteins, the SMI IgM kappa also reacts with several other self-antigens, including myoglobin, actin, and ssDNA. However, cotransfection of the SMI L chain with a vector encoding any one of 10 different G6-reactive Ig H chains generated transfectomas that produce IgM kappa antibodies without detectable polyspecific autoantibody activity. These results indicate that polyspecific antiself-reactivity of G6/17.019-reactive Ig is dependent on the somatically generated Ig third complementarity determining region. Collectively, these studies imply that selection may be responsible for the frequent expression of polyspecific autoantibodies in CLL and early B cell ontogeny.