Transformation Of Human Lymphocytes Research Articles

Influence of Paleobacteria on the Proliferative Activity of Human Lymphocytes In Vitro

When testing the proliferative activity of 14 strains of permafrost microorganisms in the reaction of blast transformation of human lymphocytes in vitro, a strain (Alcaligenes sp.) with mitogen properties was isolated (20-fold increase in the rate of lymphocyte proliferation in comparison with the control). Four strains activated lymphocyte proliferation by 3-9 times in comparison with the control. Three strains produced substances with cytostatic properties and reduced proliferation activity by 33-43% and one strain (Bacillus sp.) almost completely suppressed phytohemagglutinin-induced lymphocyte proliferation. These data indicate that strains with a unique immunobiological potential are concentrated in the population of permafrost microorganisms that have undergone rigorous evolutionary selection.

Differentiation of lymphoblastoid-derived iPSCs into functional cardiomyocytes, neurons and myoblasts

Human induced pluripotent stem cells (hiPSCs) are a valuable tool for investigating complex cellular and molecular events that occur in several human diseases. Importantly, the ability to differentiate hiPSCs into any human cell type provides a unique way for investigating disease mechanisms such as complex mental health diseases. The in vitro transformation of human lymphocytes into lymphoblasts (LCLs) using the Epstein-Barr virus (EBV) has been the main method for generating immortalized human cell lines for half a century. However, the derivation of iPSCs from LCLs has emerged as an alternative source from which these cell lines can be generated. We show that iPSCs derived from LCLs using the Sendai virus procedure can be successfully differentiated into cardiomyocytes, neurons, and myotubes that express neuron- and myocyte-specific markers. We further show that these cardiac and neuronal cells are functional and generate action potentials that are required for cell excitability. We conclude that the ability to differentiate LCLs into neurons and myocytes will increase the use of LCLs in the future as a potential source of cells for modelling a number of diseases.

The Presence of Defective Epstein-Barr Virus (EBV) Infection in Patients with EBV-Associated Hematological Malignancy

IntroductionEpstein-Barr virus (EBV) is a double-stranded DNA virus that infects >95% of the human population and is associated with a substantial risk of cancer development. Most infections in children and adolescents are asymptomatic or result in infectious mononucleosis; however, in some patients, EBV is associated with various hematological malignancies including Burkitt lymphoma, diffuse large B-cell lymphoma (DLBCL), and extranodal NK/T-cell lymphoma. EBV infection is also present in a portion of epithelial cell neoplasms such as gastric cancer and nasopharyngeal carcinoma. Despite the large population risk of cancer associated with EBV, it is poorly understood why only a small subset of EBV-infected individuals develop neoplasms, while others do not.Patients and MethodsWe designed a target enrichment system to capture several EBV strains including the Akata strain, which is responsible for the majority of EBV infections in Japan. We analyzed the genomes of EBV strains in 139 patients with various EBV-associated diseases and 17 EBV-positive cell lines. Next-generation sequencing reads were aligned to the Akata reference genome to analyze nucleotide variations, copy number alterations, and structural variations including sequence insertions in the human genome. The institutional review board of Nagoya University Graduate School of Medicine approved this study.ResultsWe identified a median of 645 single nucleotide variants (SNVs) in the EBV genomes, 78% of which affected coding sequences. SNVs in coding sequences were significantly biased toward synonymous variants, suggesting negative selection pressure. The SNVs detected in noncoding sequences were enriched in two evolutionarily conserved viral noncoding RNAs (EBER1 and EBER2), particularly in the PAX5-binding domain of EBER2. However, most SNVs identified in the EBV genome do not seem to affect the development of neoplasms, as hierarchical clustering of EBV genomes from neoplastic and non-neoplastic diseases based on SNVs revealed no significant association between the EBV strain and disease type.In addition to SNVs, we identified frequent intragenic deletions in the EBV genomes of patients with EBV-positive DLBCL (10/14, 71%), extranodal NK/T-cell lymphoma (10/23, 43%), chronic active EBV infection (27/77, 35%), and other EBV-associated neoplasms (2/7). Such deletions were also identified in several EBV-associated cell lines (6/17), but not in non-neoplastic diseases such as infectious mononucleosis (0/4) and post-transplant lymphoproliferative disorders (0/14), suggesting a unique role of these mutations in the neoplastic proliferation of EBV-infected cells. Frequent deletions were detected in BamHI A rightward transcripts microRNA clusters (31/156), which suppress viral transcription factors (BZLF1 and BRLF1) required for the lytic reactivation of EBV. Deletions also were associated with several genes essential for virus production (20/156). These observed deletions are thought to upregulate lytic cycle-associated genes, some of which benefit neoplasms by inducing genomic instability and immune escape and mitigate cell damage caused by the production of viral particles. In fact, deletion of one essential gene, BALF5, resulted in upregulation of the lytic cycle and promotion of lymphomagenesis in a xenograft model.DiscussionAlthough the essential roles of several latency-associated genes, such as LMP-1 and EBNA-2, in EBV-mediated immortalization and transformation of human lymphocytes have long been discussed, our finding raises the possibility that lytic cycle-associated genes also contribute to lymphomagenesis. This agrees with reports that lytic cycle-associated genes are expressed in Burkitt lymphoma, DLBCL, and chronic active EBV infection, and that BZLF1-deficient lymphoblastoid cells exhibit significantly impaired tumorigenicity in mice. In addition, essential gene deletions lead to the protection of EBV-infected cells from lysis. Further studies are warranted to exploit these findings for the design of novel therapeutics for EBV-associated neoplasms. DisclosuresKiyoi:Sumitomo Dainippon Pharma Co., Ltd.: Research Funding; Novartis Pharma K.K.: Research Funding; Phizer Japan Inc.: Research Funding; Sanofi K.K.: Research Funding; Kyowa Hakko Kirin Co., Ltd.: Research Funding; Celgene Corporation: Research Funding; Eisai Co., Ltd.: Research Funding; Astellas Pharma Inc.: Research Funding; Takeda Pharmaceutical Co., Ltd.: Research Funding; Otsuka Pharmaceutical Co., Ltd.: Research Funding; Chugai Pharmaceutical Co., Ltd.: Research Funding; Nippon Shinyaku Co., Ltd.: Research Funding; FUJIFILM Corporation: Research Funding; Zenyaku Kogyo Co., Ltd.: Research Funding; Bristol-Myers Squibb: Honoraria. Nakamura:Roche/Chugai,: Research Funding; Kyowa-Kirin: Research Funding.

Expression of latent membrane proteins in Epstein‑Barr virus-transformed lymphocytes invitro.

Infection with Epstein-Barr virus (EBV) induces activation and proliferation of Blymphocytes. Detection of latent membrane protein (LMP)-1 is used to identify the proliferative ability of B cells. However, changes in the expression levels of the three LMPs during EBV-induced Blymphocyte transformation, have not yet been reported. In the present study, the expression levels of LMP-1, LMP-2A and LMP-2B were compared between EBV-transformed Blymphocytes and paired normal lymphocytes. Seven lymphoblast cell lines were established by EBV infection of normal human lymphocytes invitro. The expression levels of LMP genes and LMP-1 protein were determined using quantitative (q)PCR and western blotting in lymphoblasts and normal lymphocytes, respectively. The expression of LMP1, LMP-2A and LMP-2B genes was significantly upregulated in EBV-induced lymphoblasts compared with the normal lymphocytes. The LMP-1 protein level was also significantly increased in EBV-transformed B lymphocytes. Expression of LMP1, LMP-2A and LMP-2B genes was significantly upregulated in EBV-induced lymphoblasts, suggesting LMP genes are important in the transformation of human lymphocytes.

Species restriction of Herpesvirus saimiri and Herpesvirus ateles: Human lymphocyte transformation correlates with distinct signaling properties of viral oncoproteins

The potential of Herpesvirus saimiri (HVS) subgroups A, B and C and Herpesvirus ateles (HVA) to transform primary T cells to permanent growth in vitro is restricted by the primate host species and by viral variability represented by distinct viral oncoproteins. We now addressed the relation between the transforming potential of the different viruses and the signaling pathways activated by transiently expressed oncoproteins. Marmoset lymphocytes were transformed by all HVS subgroups as well as HVA, while transformation of human cells was restricted to HVS-C and, unexpectedly, HVA. NF-κB and Src-family kinase (SFK) activity was required for survival of all transformed lymphocytes. Accordingly, NF-κB was induced by oncoproteins of all viruses. In contrast, SFK-related signaling was detectable only for oncoproteins of HVS-C and HVA. Thus, the restricted transformation of human lymphocytes likely correlates with the specific SFK targeting by these oncoproteins. These results will enable further studies into novel SFK effector mechanisms relevant for T-cell proliferation.

Inhibition of human lymphocyte transformation by two aryloxyalkylamidines.

The incorporation of [3H]thymidine into human lymphocytes stimulated by phytohaemagglutinin (PHA) was inhibited by anilino-N-2-m-chlorophenoxypropylacetamidine (501C) and xylamidine. These amidines antagonize 5-HT, but 5-HT did not alter [3H]thymidine incorporation. 501C inhibited PHA-induced lymphocyte transformation as observed by [3H]thymidine incorporation, [3H]uridine incorporation, [3H]leucine incorporation, DNA content, potassium content, and histological examination. 501C also inhibited increased [3H]thymidine incorporation in human mixed lymphocyte cultures. The IC50 of 501C for inhibition of these processes lay between 4 and 8 microM. When added late in culture (after 6-8 h) 501C was less effective. Possible mechanisms by which 501C inhibits transformation are discussed.

Heme oxygenase‐1 inhibits T cell‐dependent skin inflammation and differentiation and function of antigen‐presenting cells

Heme oxygenase-1 (HO-1) is increased in psoriatic skin. We asked for the impact of physiological and pharmacological HO-1 induction on skin immunity and the mechanisms involved in HO-1-induced immunomodulation. We found cutaneous HO-1 expression upregulated comparable with suppressors of cytokine signalling (SOCS)1 and SOCS3 in psoriasis and atopic eczema and temporarily increased in murine ovalbumin-induced late phase reaction (LPR) and 2,4-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity (CHS). Cutaneous inflammation was enhanced by HO-1 inhibition and was abrogated by treatment with the HO-1 inducer cobaltic protoporphyrin (CoPP) both when applied around sensitization or before challenge. HO-1 inhibition specifically prevented the anti-inflammatory CoPP effect. CoPP inhibited T cell proliferation in splenocytes of treated mice and in human mixed leukocyte reaction and lymphocyte transformation test. CoPP induced HO-1 in antigen-presenting cells and depressed monocytic accessory molecule expression and the differentiation and maturation of monocyte-derived dendritic cells (MDDC). It decreased tumor necrosis factor (TNF)-alpha and interleukin (IL)-12 production while increasing IL-10 secretion. The antigen-presenting capacity was diminished in CoPP-treated and HO-1-transduced MDDC. We demonstrate for the first time the physiological role of HO-1 in the limitation of skin inflammation and implement pharmacological HO-1 induction as a therapeutic approach for T cell-dependent inflammatory dermatoses. Suppression of antigen-presenting cells may represent a main anti-inflammatory mechanism of HO-1.

381 POSTER HSP27 as a novel target in Non-small cell lung cancer with particular implications for migration and metastasis

The potential of Herpesvirus saimiri (HVS) subgroups A, B and C and Herpesvirus ateles (HVA) to transform primary T cells to permanent growth in vitro is restricted by the primate host species and by viral variability represented by distinct viral oncoproteins. We now addressed the relation between the transforming potential of the different viruses and the signaling pathways activated by transiently expressed oncoproteins. Marmoset lymphocytes were transformed by all HVS subgroups as well as HVA, while transformation of human cells was restricted to HVS-C and, unexpectedly, HVA. NF-κB and Src-family kinase (SFK) activity was required for survival of all transformed lymphocytes. Accordingly, NF-κB was induced by oncoproteins of all viruses. In contrast, SFK-related signaling was detectable only for oncoproteins of HVS-C and HVA. Thus, the restricted transformation of human lymphocytes likely correlates with the specific SFK targeting by these oncoproteins. These results will enable further studies into novel SFK effector mechanisms relevant for T-cell proliferation.

The effect of calyx infusion of hibiscus sabdariffa l. On t-cells-mediated immune response in mitogen-induced blastogenesis of human lymphocytes in vitro

Free radical production and disturbance in the redox status may modulate the expression of a variety of immune and inflammatory molecules. Antioxidants could inhibit the proliferation of T lymphocytes induced by mitogens. The aim of this study was to investigate the effect of the infusion of dried calyx of Hibiscus sabdariffa L. on T-cell-mediated immune response. We examined the effect of the infusion on spontaneous and mitogen-induced blast transformation of human lymphocytes in vitro. Peripheral blood lymphocytes from heparinised venous blood of healthy subjects (n=17) were examined. Five and 10 mg ml-1 phytohemagglutinin (PHA) and 5 mg ml-1 pokeweed mitogen (PWM) were added. Depending on the concentration, calyx infusion of H. sabdariffa decreased mitogen-induced blastogenesis in normal subjects. It did not affect, however, the level of spontaneous proliferation of human lymphocytes in vitro. The infusion of hibisci flos may alleviate over-stimulated condition of the immune system in hypersensitivity ...

Expression of the negative co-stimulatory ligand sCD152 in the yeast, Pichia pastoris, and its regulation of antigen specific immune responses

CD152, a ligand expressed on the surface of the activated T cells that inhibits co-stimulatory signals, is associated with negative regulation of T-cell activation in the antigen-presenting process. In order to interfere with immune signal transmission, obtain functional proteins with specific immunosuppressive effects, and regulate the immune response, we cloned the full-length extracellular domain of CD152 into the expression vector pPICTLA and transformed Pichia pastoris GS115 cells by electroporation. Yeast colonies expressing and secreting large quantities of the extracellular soluble fragment of CD152 (sCD152) were isolated, and the protein was purified and used in assays designed to investigate the ability of sCD152 to regulate the immune system. In a series of antigen specific immune response interference tests in mice, human allogeneic mixed lymphocyte reaction and antigen specific lymphocyte transformation tests, we found that sCD152 had a marked immunosuppressive effect. This protein reduced antibody titer in mice immunized with BSA, significantly inhibited the killing of antibody-dependent cytotoxicity and CTL-mediated donor target cells, and reduced the expression of IL2 in mice. In the absence of exposure of sCD152, long-term stimulation (>5 days) by the same antigen in vivo partially restored the immune response-correlated stimulation index (SI), showing the characteristics of a primary immune response. Following the deletion of sCD152, however, there was no obvious inhibitory effect on the primary immune response triggered by the nonrelevant antigen OVA, indicating that sCD152 had an antigen-specific immunosuppressive effect and that the inhibitory effect of sCD152 required the co-administration of antigen. These findings suggest that sCD152 may have clinical potential as an immunosuppressive agent.

Increased cyclooxygenase-2 (COX-2): a potential role in the pathogenesis of lymphoma

B cell lymphomas are a diverse group of clinicopathologic diseases with an increasing incidence. As with other malignancies, the accumulation of genetic abnormalities are required for malignant transformation of human lymphocytes. Cyclooxygenase-2 (COX-2) is a key biosynthetic enzyme in prostaglandin synthesis and has been implicated in the pathogenesis of numerous malignancies including colon, breast, and lung cancer. There is little data on the potential role of COX-2 in lymphoma pathogenesis. In this study, several B lymphoma cell lines and primary B cells obtained from normal volunteer controls were examined for COX-2 protein expression. Immunoblot analysis demonstrated between an approximately 2.2–4.3-fold increase in COX-2 protein expression relative to primary B cells in all lymphoma cell lines examined. Increased COX-2 phosphorylation was found in the BJAB, BL41, and Raji cells whereas the levels in Daudi, Namalwa, and Ramos did not differ from that of primary B cells. Treatment with 25–100 μM celecoxib (CEL) resulted in decreased proliferation as measured by [ 3 H] thymidine in all cell lines examined, and the effect was dose-dependent, and not significantly enhanced by chlorambucil (CHL). The effect of COX-2 inhibition on apoptosis in lymphoma cells was examined and revealed apoptotic induction of greater than 85% in all cell lines examined at 50 μM celecoxib. The pro-apoptotic effect was dose-dependent, and was not significantly enhanced by chlorambucil. Examination of apoptosis-related proteins by immunoblot analysis revealed levels of BCL-2, BCL-X L, and Bax to be unaffected by celecoxib. In contrast, levels of Akt, MCL-1, and phosphorylated SAP-kinase were all decreased after incubation with 50 μM celecoxib. These findings suggest that increased COX-2 expression and activity, contributes to the pathogenesis of B cell lymphomas and point to a possible role for COX-2 inhibition in their treatment.

Analysis of human CD4 T lymphocyte proliferation induced by porcine lymphoblastoid B cell lines.

This study was undertaken to characterize the two porcine lymphoblastoid cell lines L23 and L35, derived from a pig inoculated by the retrovirus Tsukuba-1, and to determine how they induce a strong human lymphocyte proliferation. Phenotypic characterization was performed by flow cytometry and reverse transcriptase-polymerase chain reaction analyses. Xenogeneic mixed lymphocyte reactions (XMLR) were performed using unfractionated human peripheral blood mononuclear cells (huPBMC) and purified CD4+ T lymphocytes as responding cells, in the presence of blocking antibodies and fusion proteins. The immunoglobulin genes were demonstrated to be rearranged in L23 and L35 cell lines, in agreement with the expression of a B cell phenotype. Both induced a similar proliferation of huPBMCs and purified human CD4+ lymphocytes from adult or cord blood (naïve cells). Proliferation of CD4+ T lymphocytes was completely blocked by anti-SLA-DR plus anti-SLA-DQ mAbs, excluding human lymphocyte transformation by porcine viruses. The frequency of proliferative precursors was inconsistent with that induced by a retroviral superantigen but similar to classical direct xenoantigen presentation as observed with other porcine antigen-presenting cells. Extensive analysis of costimulatory signals led to the identification of the CD28 pathway, in agreement with membrane expression of B7 molecules on L23 and L35 cells, and of the CD2 pathway in L35 cells. These two porcine lymphoblastoid cell lines have been further characterized and clearly identified as belonging to the B cell lineage. By expressing major histocompatibility complex class II antigens and costimulatory molecules, they induce a vigorous proliferative response of human CD4+ lymphocytes through a direct presentation pathway.

Synthesis and distribution of glycosaminoglycans in human leukemic B- and T-cells and monocytes studied using specific enzymic treatments and high-performance liquid chromatography.

Identification of glycosaminoglycans (GAGs) synthesized by three human leukaemic cell lines-Jurkat (T-cell leukaemia), Daudi (Burkitt's lymphoma, B-cell leukaemia) and THP-1 (acute monocytic leukemia)-and normal peripheral blood mononuclear cells (PBMC) and their distribution among cell membrane and culture medium were studied. GAGs were isolated using ion-exchange chromatography on DEAE-Sephacel and their composition and fine chemical structure were studied using high-performance liquid chromatography with radiochemical detection. All cell lines synthesize chondroitin sulphate (CS) and heparan sulphate (HS) in both cell membrane and culture medium. No hyaluronan was detected using treatment with specific lyases and highly sensitive HPLC methodology. CS is the major secreted GAG in all cell lines tested and the major cell retained GAG in Jurkat and Daudi. HS is the major GAG in the cell membrane of THP-1. The amounts of distinct GAGs synthesized by all cancer cell lines differ from those produced by normal PBML indicating a major role of GAGs in malignant transformation of human lymphocytes and monocytes.

Effects of arsenic on blast transformation and DNA synthesis of human blood lymphocytes

Effects of inorganic arsenicals on DNA synthesis in unsensitized human blood lymphocytes were biphasic: the chemicals at very low concentrations enhanced blast transformation and DNA synthesis, whereas higher concentrations inhibited the transformation and DNA synthesis. The concentrations of arsenicals at which the maximum stimulating effect was found were 1 × 10 −5 M, 1 × 10 −6 M or 2 × 10 −6 M, and 0.8 × 10 −6 M or 1 × 10 −6 M for sodium arsenite exposure of 1 h, 3 days and 6 days, respectively; for sodium arsenate, 1 × 10 −5 M, 1 × 10 −5 M, and 2 × 10 −6 M or 5 × 10 −6 M, respectively. Arsenicals must be present for the entire 6 days culture period to produce maximum stimulation of blast transformation of human lymphocytes. The longer exposure of the lymphocytes to arsenicals, the lower the concentrations of arsenicals at which the maximum stimulating effect was found. The stimulating effect of trivalent arsenic (sodium arsenite) was stronger than pentavalent arsenic (sodium arsenate).

Regulation ofin vitro human lymphocyte blast transformation associated with γ-globulin fraction containing a carbohydrate component

Carbohydrate-enriched components were isolated from human serum γ-globulin by chelation of associated transition metals. Similar to the initial γ-globulin preparation, these components stimulatein vitro blast transformation of human lymphocytes from healthy donors and inhibit subsequent phytomitogen-induced lymphocyte blast transformation.

Role of cellular tumor necrosis factor receptor-associated factors in NF-kappaB activation and lymphocyte transformation by herpesvirus Saimiri STP.

The STP oncoproteins of the herpesvirus saimiri (HVS) subgroup A strain 11 and subgroup C strain 488 are now found to be stably associated with tumor necrosis factor receptor-associated factor (TRAF) 1, 2, or 3. Mutational analyses identified residues of PXQXT/S in STP-A11 as critical for TRAF association. In addition, a somewhat divergent region of STP-C488 is critical for TRAF association. Mutational analysis also revealed that STP-C488 induced NF-kappaB activation that was correlated with its ability to associate with TRAFs. The HVS STP-C488 P10-->R mutant was deficient in human T-lymphocyte transformation to interleukin-2-independent growth but showed wild-type phenotype for marmoset T-lymphocyte transformation in vitro and in vivo. The STP-C488 P10-->R mutant was also defective in Rat-1 fibroblast transformation, and fibroblast cell transformation was blocked by a TRAF2 dominant-negative mutant. These data implicate TRAFs in STP-C488-mediated transformation of human lymphocytes and rodent fibroblasts. Other factors are implicated in immortalization of common marmoset T lymphocytes and may also be critical in the transformation of human lymphocytes and rodent fibroblasts.

Induction and inhibition of human lymphocyte transformation by the lectin from the red marine alga Amansia multifida

Lectins are powerful stimulants of quiescent peripheral blood lymphocytes. They can induce blast transformation leading to mitosis of these cells in vitro. We report here the dose-dependent proliferative curve for human peripheral blood monouclear cells (PBMC) stimulated by the lectin amansin, from Amansia multifida. Amansin stimulated proliferation of (PBMC) at relatively low concentrations (3.12 to 12.5 µg mL-1). We observed also a gradual reduction in mitogenic capacity with progressive increase in the lectin concentration above 12.5 µg mL-1. This decrease in the mitogenic potential did not result from a toxic effect on the cells, and was predominant at a lectin concentration above 50 µg mL-1. This decrease in lymphocyte proliferation could be blocked by avidin and could not be overcome by IL-2 or another lectin (Con Br) at stimulatory concentrations. Additionally, we observed that cells incubated at stimulatory concentrations of amansin produced IFN-γ. Analysis of the culture supernatants established a direct correlation between the IFN-γ and the mitogenic and anti-mitogenic capacity of amansin.

Na, K-ATPase pump in activated human lymphocytes: on the mechanisms of rapid and long-term increase in K influxes during the initiation of phytohemagglutinin-induced proliferation

Functional expression of Na, K-ATPase pump as determined by ouabain-sensitive Rb influxes has been investigated in human peripheral blood lymphocytes, activated by phytohemagglutinin (PHA) from resting state to proliferation. It is found that a rapid twofold elevation of ouabain-sensitive Rb influx in response to PHA is followed by a long-term increase in pump activity, which precedes the DNA synthesis and is temporally related to the growth phase of mitogenic response. Unlike the early pump activation, the late enhanced pump activity is not the result of elevated cell Na content, it is inhibited by cycloheximide and requires new protein synthesis. Actinomycin D and α-amanitin, in doses, which suppress the PHA-induced increase in the RNA synthesis, do not abolish the elevated Rb influx until 20–24 h of mitogenic activation and inhibit the late, growth-associated increase in Rb influx. It is concluded that (1) in mitogen-activated cells both short- and long-term control is involved in the enhanced pump activity, and (2) translational and transcriptional mechanisms may contribute to the long-term up-regulation of Na, K-ATPase pump during blast transformation of human lymphocytes.

Safety of growth hormone after treatment of a childhood malignancy.

The use of growth hormone therapy in children with radiation-induced growth hormone (GH) deficiency is widely accepted, but the safety of this mitogenic hormone, particularly in children previously treated for cancer, continues to cause concern. A variety of malignant tumours have been induced in animals exposed to supraphysiological doses of GH, whereas hypophysectomised animals appear protected from carcinogen-induced neoplasms. Growth hormone and insulin-like growth factor-1 have been shown to stimulate both proliferation and transformation of normal and leukaemic human lymphocytes in vitro when used in supraphysiological doses. Despite the theoretical arguments, there is no evidence of an increased risk of tumour recurrence following GH therapy in replacement dosage in children previously treated for a malignancy.

Hairy cell transformation of human peripheral blood lymphocytes by Coxiella burnetii.

Hairy cell (HC) transformation of human peripheral blood lymphocytes (PBL) by Coxiella burnetii was studied to clarify the significance of persistency of C. burnetii in a hairy cell line (designated "TOL"). TOL cells which exhibited HC characteristics in hairy cell leukemia (HCL) were persistently infected with C. burnetii. Two strains of C. burnetii, our isolate from TOL cells and the original isolate in 1935, the Nine Mile strain from American Type Culture Collection (ATCC, U.S.A), were inoculated to PBL cultures. HC transformation not only by our isolates (87%) but also by Nine Mile strain (100%) was demonstrated in an average of 20 days. The original observation that Coxiella induced HC transformation in vitro was also confirmed in experiments with PBL exposed to C. burnetii in vivo. Spontaneous development of HC were observed in cultures of PBL only from coxiellemic cases (12/24) but not from C. burnetii negative cases (0/57). All HC cell lines (34) as determined by their morphology and cytochemical markers of HC in HCL remained infected with C. burnetii invariably.