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Biomedical subjects

V Pistoia

Publications and source records attributed to V Pistoia.

At least 37 records · Page 2Linked to original sources
PubMed2000

T cell clones raised from chronically infected healthy humans by stimulation with Toxoplasma gondii excretory-secretory antigens cross-react with live tachyzoites: characterization of the fine antigenic specificity of the clones and implications for vaccine development.

Excreted-secreted Ags (ESA) of Toxoplasma gondii (Tg) play an important role in the stimulation of the host immune system in both acute and chronic infections. To identify the parasite Ag(s) involved in the maintenance of T cell-mediated long term immunity, 40 ESA-specific T cell clones were derived from three chronically infected healthy subjects. All the clones were CD4+ and recognized both ESA and live tachyzoites in a HLA-DR-restricted manner. Conversely, CD4+ tachyzoite-specific T cell clones from the same subjects proliferated in response to ESA, pointing to shared immunodominant Ags between ESA and Tg tachyzoites. By T cell blot analysis using SDS-PAGE-fractionated parasite extracts, the following patterns of reactivity were detected. Of 25 clones, 6 recognized Tg fractions in the 24- to 28-kDa range and proliferated to purified GRA2, 5 reacted with Tg fractions in the 30- to 33-kDa range; and 4 of them proved to be specific for rSAg1. Although surface Ag (SAg1) is not a member of ESA, small amounts of this protein were present in ESA preparation by Western blot. Of 25 clones, 8 responded to Tg fractions in the 50- to 60-kDa range but not to the 55-kDa recombinant rhoptries-2 parasite Ag, and 6 did not react with any Tg fraction but proliferated in response to either ESA or total parasite extracts. In conclusion, CD4+ T cells specific for either ESA (GRA2) or SAg1 may be involved in the maintenance of long term immunity to Tg in healthy chronically infected individuals.

Animals↗
PubMed2000

Flow cytometric and functional characterization of AC133+ cells from human umbilical cord blood.

AC133+ cells may represent an alternative source of transplantable haemopoietic progenitor cells to CD34+ cells. Here, we have addressed the characterization of umbilical cord blood (UCB) AC133+ cells and compared their immunophenotypic and functional features with those of UCB CD34+ cells. UCB AC133+ and CD34+ cell fractions were purified by magnetic cell sorting, analysed by flow cytometry, tested for their content in blast cell colony-forming units (CFU-Bl), erythroid and granulocyte-macrophage colony-forming units before and after expansion in the presence of various haemopoietic growth factor combinations. Median AC133+ cell yield was 62.3%, and median AC133+ population purity was 97.9%. AC133+ cells were found to contain significantly more CFU-Bl than CD34+ cells; furthermore, the replating efficiency, i.e. the number of CFU-Bl capable of generating secondary colonies, was higher in the former than in the latter cells. Both AC133+ and CD34+ cells displayed an increased ability to give rise to committed progenitors after 7-day expansion in liquid cultures. These data suggest that the AC133+ cell subset is a heterogeneous pool of immature and more differentiated cells that can be maintained and expanded in well-defined culture conditions. In comparison with CD34+ cells, UCB AC133+ cells appear to contain a higher number of early haemopoietic progenitors.

AC133 Antigen↗
PubMed2000

Inhibitory activity of fenoterol on Dermatophagoides-, Parietaria-, tetanus-toxoid-, and Candida albicans-stimulated blood mononuclear cells: differences in beta2-adrenoreceptor stimulation but not in cell apoptosis.

beta2-adrenoreceptor agonists have the ability to downregulate in vitro the proliferative response of peripheral blood mononuclear cells (BMCs). This activity could be related to a variety of beta2-adrenoreceptor-mediated functions, including induction of cell apoptosis in activated T-cells. To test this hypothesis, BMCs from atopic subjects, sensitized to house dust mites (Dermatophagoides [Der p]) and/or to Parietaria were incubated with fenoterol (10(-8)-10(-5) M) in the presence of (a) purified allergen extracts (Der p [5 microg/mL] or Parietaria [5 microg/mL]) or (b) antigens (tetanus toxoid [1 microg/mL] or Candida albicans [5 x 10(5) bodies/mL]). The BMC proliferation was assessed by [3H] thymidine incorporation and cell apoptosis was assessed by evaluating DNA fragmentation by a fluorescence technique, using propidium iodide. In cultures stimulated with Der p or with Parietaria, fenoterol induced a dose-dependent inhibition of BMC proliferation, significant also at the lowest concentration tested (10(-8) M) (p < 0.05, each comparison). In contrast, the inhibitory activity of the drug on tetanus-toxoid-stimulated BMCs was significant only at the highest dose tested (10(-5)M) (p < 0.05), whereas no effect was seen when BMCs were stimulated with C. albicans extract (p > 0.05). The different inhibitory efficacy of fenoterol appeared to be related to the degree of activation of beta2-adrenoreceptors on the different BMC populations that responded to the different stimuli. Indeed, in the presence of fenoterol (10(-6) and 10(-5)M), a significant increase in cyclic adenosine monophosphate (cAMP) levels was seen in Der p- or Parietaria-stimulated cells (p < 0.05; each comparison), but not in cell cultures stimulated with tetanus toxoid or with C. albicans extracts (p > 0.05; each comparison). Finally, the percentage of cells with fragmented DNA was lower in cultures stimulated with Der p or Parietaria than in those stimulated with tetanus toxoid or C. albicans, and the presence of fenoterol did not modify cell apoptosis (p > 0.05; each comparison). Thus, the different inhibitory activity of fenoterol on BMCs activated by allergens (Der p or Parietaria) or by antigens (tetanus toxoid or C. albicans) seems to be related to differences in beta2-adrenoreceptor expression and/or function in the different antigen-specific T-cell subsets, but it is not influenced by changes in cell apoptosis.

Adrenergic beta-Agonists↗
PubMed2000

Late Epstein-Barr virus infection of a hepatosplenic gamma delta T-cell lymphoma arising in a kidney transplant recipient.

BACKGROUND AND OBJECTIVE: gd T-cell lymphomas are only exceptionally observed in transplanted patients. Aim of this study was the detailed characterization of one such case. DESIGN AND METHODS: The patient developed spontaneous splenic rupture six years after kidney transplantation. The splenic red pulp was infiltrated by medium-sized and large lymphoid cells with two or more nucleoli. At autopsy, similar lymphoid cells infiltrated the hepatic sinusoids. Histologic, immunologic and molecular studies were carried out. RESULTS: By immunohistochemistry, the atypical lymphoid cells were found to express CD3, CD45 and CD43, indicating their T-lineage origin. Approximately 99% of spleen mononuclear cells (MNC) were CD3(+), gammadelta TcR+, CD4-, CD8-, alphabeta TcR-. A clonal gammadelta TcR rearrangement (Vgamma1-Jgamma1.3/2.3-Cgamma2; Vdelta1-Ddelta2-Jdelta1) was detected. The final diagnosis was peripheral T-cell lymphoma, hepato-splenic gammadelta-type. EBV infection of spleen MNC was documented by molecular studies. However, in situ hybridization for EBER-1 (EBV-RNA) showed that only a minority of malignant lymphoid cells (5-7%) were EBV-infected. INTERPRETATION AND CONCLUSIONS: It is concluded that EBV infection was as a late event involving an already transformed gd T-cell clone.

Adult↗
PubMed2000

Tumor necrosis factor induced adhesion molecule serum concentrations in Henoch-Schönlein purpura and pediatric systemic lupus erythematosus.

OBJECTIVE: Animal models of immune complex mediated tissue injury have shown that tumor necrosis factor (TNF) and TNF induced adhesion molecules play an important role in the pathogenesis of tissue damage mediated by IgG, but not in that mediated by IgA, immune complexes. We compared possible differences in the behavior of 2 TNF induced adhesion molecules (VCAM-1 and ICAM-1) in Henoch-Schönlein purpura (HSP), which is characterized by the formation of IgA immune complexes, versus systemic lupus erythematosus (SLE), which is mostly associated with the vascular deposition of IgG immune complexes. METHODS: Serum concentrations of soluble (s)VCAM-1 and ICAM-1 were determined by ELISA methods in 20 patients with pediatric SLE showing variably active disease, 20 active patients with active HSP, and 19 healthy controls. TNF-alpha as well as p55 and p75 soluble receptors (sTNF-R) were simultaneously tested by enzyme amplified sensitivity immunoassay in 22 patients (12 SLE, 10 HSP). RESULTS: Serum sVCAM-1 concentration was significantly higher in patients with SLE (mean +/- SD, 608 +/- 76 ng/ml), than in patients with HSP (501.9 +/- 63.3 ng/ml) and controls (446.8 +/- 139.2 ng/ml) (p < 0.001). In SLE patients, sVCAM-1 correlated positively with ESR (r = 0.45, p = 0.02) and negatively with C4 serum levels (r = -0.57, p = 0.004), platelets (r = -0.38, p = 0.03), and lymphocyte count (r = -0.42, p = 0.03). No differences in sICAM-1 serum concentrations were detected among SLE, HSP, or control groups. Soluble VCAM, but not sICAM-1, showed a positive correlation with TNF-alpha (r = 0.71, p = 0.01), p55 (r = 0.63, p = 0.02), and p75 (r = 0.7, p = 0.01) sTNF-R serum concentrations in SLE, but not in patients with HSP. CONCLUSION: Our study provides additional evidence of a possible differential involvement of TNF and TNF induced adhesion molecules in the pathogenesis of tissue damage between pediatric SLE and HSP.

Adolescent↗
PubMed2000

Cytokine gene expression and T-cell proliferative responses in lymph node mononuclear cells from children with early stage human immunodeficiency virus infection.

BACKGROUND AND OBJECTIVES: The immunologic events taking place in secondary lymphoid tissue from children with early stage human immunodeficiency virus (HIV) infection are poorly understood. The aim of this study was to investigate cytokine gene expression and proliferative responses in lymph node (LN) biopsies from five children with early stage HIV infection, in the context of LN morphology and viral load. DESIGN AND METHODS: The design of the study was approved by the local Ethical Committee. Cytokine gene expression was studied in LN biopsies and in paired peripheral blood (PB) samples from HIV-infected children by reverse transcriptase-polymerase chain reaction. T-cell proliferation was assessed by 3H-thymidine incorporation. Viral burden in germinal centers was assessed by video densitometric analysis following immunohistochemical staining for HIV p24. RESULTS: Interleukin (IL)-2, IL-4 and IL-5 mRNA were not detected in any LN or PB sample from HIV-infected children. Interferon (IFN)-gamma mRNA was found only in CD8+ cells. IL-12 p35, IL-10, transforming growth factor-(TGF)-beta1, regulated on activation normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta and IL-16 transcripts were detected in all samples. Proliferation of LN and PB mononuclear cells to polyclonal mitogens and soluble (recall and HIV-related) antigens was impaired as compared with the responses in a group of age-matched healthy controls. INTERPRETATION AND CONCLUSIONS: Changes in cytokine gene expression and T-cell proliferative responses are already detectable in lymph nodes from HIV-infected children at an early stage of disease.

Child↗
PubMed1999

Ultrastructural and functional studies of the interaction between IL-12 and IL-2 for the generation of lymphokine-activated killer cells.

IL-12 promotes generation of LAK activity in short-term-cultured NK cells, but information on the structure and function of IL-12-induced LAK cells is not yet available. The latter issues have been here investigated with emphasis on interactions between IL-12 and IL-2. Peripheral blood mononuclear cells (MNC) exposed to IL-12 for 5-7 days displayed a decrease in the amount and density of the matrix of large granular lymphocyte (LGL)-associated granules. In cells cultured with IL-12 and IL-2 for 5-7 days, empty vacuoles were predominant and the electron-dense matrix was scanty. In MNC incubated with IL-2 for 5-7 days, most granules were loaded with electron-dense matrix. IL-12 and IL-2 displayed an additive effect on LAK cell cytotoxicity until approximately 48 h in culture which was followed by a sharp decline. Immunocytochemical and biochemical studies demonstrated that MNC cultured for 5-7 days with IL-12 and IL-2 displayed downregulated perforin expression and upregulated granzyme B expression. Fas ligand expression was virtually undetectable in MNC cultured for 5-7 days with or without cytokines. It appears that perforin downregulation plays a major role in the reduced cytotoxicity of MNC cultured with IL-12 and IL-2 for 5-7 days.

Cell Differentiation↗
PubMed1999

rC5a directs the in vitro migration of human memory and naive tonsillar B lymphocytes: implications for B cell trafficking in secondary lymphoid tissues.

Human C5a is a potent chemoattractant for granulocytes, monocytes, and dendritic cells. In mice C5a has been shown to be chemotactic for germinal center (GC) B cells. To date, no information is available on the effects of C5a on human B cell locomotion. Here we demonstrate that rC5a increases polarization and migration of human tonsillar B cells. The locomotory response was due to both chemokinetic and chemotactic activities of rC5a. Moreover, memory and, at a lesser extent, naive B cell fractions from purified tonsillar populations displayed rC5a-enhanced migratory properties, whereas GC cells did not. Flow cytometry revealed C5aR (CD88) on approximately 40% memory and 10% naive cells, respectively, whereas GC cells were negative. Immunohistochemistry showed that a few CD88+ cells were of the B cell lineage and localized in tonsillar subepithelial areas, where the majority of memory B cells settle. Pretreatment of memory B cells with the CD88 mAb abolished their migratory responsiveness to rC5a. Finally, the C5 gene was found to be expressed in naive, GC, and memory B lymphocytes at both the mRNA and the protein level. This study delineates a novel role for C5a as a regulator of the trafficking of human memory and naive B lymphocytes and supports the hypothesis that the B cells themselves may serve as source of C5 in secondary lymphoid tissues.

Antigens, CD↗
PubMed1999

Late graft failure 8 years after first bone marrow transplantation for severe acquired aplastic anemia.

A 14-year-old patient with acquired very severe aplastic anemia (VSAA) underwent bone marrow transplantation (BMT) from his HLA-identical brother. Preparative therapy was cyclophosphamide (CY) 200 mg/kg over 4 days. GVHD prophylaxis was with cyclosporin A (CsA) for a year. After an 8 year follow-up during which the patient was well with normal blood counts, graft failure occurred. At this time marrow chimerism studies demonstrated that 85% of hemopoiesis was of recipient origin. The patient was re-engrafted from the same donor after conditioning with CY 200 mg/kg over 4 days plus rabbit antithymocyte globulin (ATG) 3.5 mg/kg/day for 3 days. After 140 days follow-up he has a normal blood count. The possible causes of the graft failure are discussed. This case demonstrates that, although rarely, very late graft failure may occur after BMT for AA and highlights the need for long-term monitoring even in apparently successfully transplanted patients.

Adolescent↗
PubMed1999

Clinical and biological characteristics of immunopathological disease-related erythema nodosum in children.

We report a series of 22 children with idiopathic, drug unrelated erythema nodosum (EN) admitted to our Department. In 5 of them an history of streptococcal pharyngitis was referred; the remaining patients came to us with a diagnosis of "EN of unknown origin". Acute phase reactants, immunoglobulins, stool alpha1 antitrypsin, ANA, anti dsDNA antibodies and ANCA assay, chest roentgenogram, tuberculin test, and ophthalmologic assessment were performed in all patients. Etiologic diagnosis was made in 16 patients: Streptococcal pharyngitis (5 cases), chronic inflammatory bowel disease, IBD (3 cases), Behçet syndrome (2 cases), Yersinia enteritis (2 cases), infectious mononucleosis, atypical mycobacterial infection, immunodeficiency related infection, and SLE-like syndrome due to C4 deficiency (1 case each). We found oral/scrotal aphthae in 3 cases, gastrointestinal symptoms in 5 cases, arthritis in 3 cases. Acute phase reactants were positive in 16 patients without correlation to the underlying disease. Conversely, the increased alpha1 antitrypsin stool excretion and IgA serum concentration seemed to represent helpful indicators of IBD and Behçet syndrome, respectively. Proinflammatory cytokine pattern showed increased IL6 serum concentrations both in infectious and in non infectious disease-related EN, whereas a minor involvement of TNF was found in these patients.

Adolescent↗
PubMed1999

Peritoneal mesothelial cells produce complement factors and express CD59 that inhibits C5b-9-mediated cell lysis.

The CD59 membrane protein confers protection from C5b-9-mediated cell lysis. Because evidence exists for complement (C) activation and generation of C5b-9 in the peritoneal cavity during chronic peritoneal dialysis (CPD), we investigated, on mesothelial cell (MC) lines, the expression of CD59 and the production of C components. Four MC lines were obtained from children on CPD, and two from non uremic children. CD59 expression on MCs was investigated with anti-CD59 monoclonal antibody (mAb) and polyclonal goat immunoglobulin G (IgG). MC lines were positive for staining with anti-CD59 mAb. Western blotting analysis of MC membrane demonstrated a band with the same molecular weight as CD59. Incubation of MC with anti-CD59 mAb abrogated the protective effect of CD59 (100% cytotoxicity). C3, C4, and C6 were detected in the supernatants of MC; in non uremic MC supernatants, C5, C7, C8, and C9 were also detectable, and C4 concentration was tenfold higher. CD59 expression confers to MCs protection from C5b-9-mediated lysis. MCs produce C factors. These findings suggest that production of complement components and expression of CD59 on MCs could play a role both in peritoneal cavity infection (decreased complement production) and in peritoneal membrane damage (decreased CD59 expression and reduced remesothelialization owing to MC lysis).

CD59 Antigens↗
PubMed1998

Serum interleukin 12 concentration in juvenile chronic arthritis.

OBJECTIVES: The aim of this study was to evaluate serum interleukin (IL) 12 concentration in patients with juvenile chronic arthritis (JCA), according to disease subtype, activity, and duration. IL12 has been demonstrated to prime the selective expansion of T helper (Th) cells with a Th1-type pattern of cytokine production. METHODS: Sixty eight serum samples from 50 JCA patients (12 systemic, 12 polyarticular, 26 pauciarticular), 20 serum samples from age matched healthy controls were tested with two different immunoassays specific for total IL12 (p40 and p70 heterodimer) and for IL12 (p70) heterodimer, respectively. The following disease activity parameters were evaluated: (a) presence of arthritis at least in one joint, (b) physician global estimate of disease activity, (c) disability index according to the Childhood Health Assessment Questionnaire (CHAQ), (d) C reactive protein (CRP). RESULTS: Total IL12 (p40 and p70 heterodimer) was significantly higher in JCA active patients than in those on clinical remission and in healthy controls (p < 0.001). Conversely, detectable concentrations of IL12 (p70) heterodimer were found in three active JCA patients only. Moreover, total IL12 (p40 and p70 heterodimer) showed a significant negative correlation both with time from disease diagnosis (r = -0.29, p = 0.04) and, for the pauciarticular subgroup, with disease activity duration (r = -0.71, p < 0.001). CONCLUSIONS: This study shows that the p40 moiety of IL12 is increased in serum samples from active JCA patients, especially in the earliest phases of the disease, whereas biological active IL12 (p70) heterodimer is virtually undetectable.

Adolescent↗
PubMed1998

Prolactin and interleukin 6 in prepubertal girls with juvenile chronic arthritis.

OBJECTIVE: To evaluate prolactin (PRL) serum levels in prepubertal girls affected with 2 different subtypes of pauciarticular onset juvenile chronic arthritis (JCA) and with previous acute postinfectious arthritis in remission (AA), and to correlate the relationship of PRL versus interleukin 6 (IL-6) serum levels. METHODS: Eleven girls with antinuclear antibody (ANA) positive early onset pauciarticular JCA, 8 with ANA negative late onset pauciarticular JCA of various forms (considered to have spondyloarthropathy, SpA), and 7 who had had AA were evaluated for serum concentrations of PRL, IL-6, and thyroid hormones and presence of uveitis. All were prepubertal and without clinical or biological signs of disease activity. RESULTS: Mean serum concentrations of PRL were significantly increased in ANA positive (8.9 +/- 4.0 ng/ml) patients and in patients with SpA (7.8 +/- 2.4 ng/ml) compared to those of AA patients (4.4 +/- 0.3 ng/ml) (p = 0.01 and p = 0.025, respectively) and to controls. Both ANA positive and SpA patients showed increased mean serum concentrations of IL-6 in comparison with AA patients and controls. Significant correlation between PRL and IL-6 concentrations (r = 0.604, p = 0.002) was observed from the whole series. CONCLUSION: We found a direct correlation between serum levels of PRL and IL-6 in both ANA positive JCA patients and in ANA negative SpA patients; thus, hyperprolactinemia correlates better with the chronic course of the disease than with ANA positivity.

Adolescent↗
PubMed1998

Differences in tumor necrosis factor-alpha soluble receptor serum concentrations between patients with Henoch-Schönlein purpura and pediatric systemic lupus erythematosus: pathogenetic implications.

OBJECTIVE: Animal models of immune complex mediated tissue injury have shown different patterns of proinflammatory cytokine production according to the subtype of immunoglobulin involved. The IgA immune complex model differs from the IgG model by the lack of involvement of tumor necrosis factor (TNF) in the pathogenesis of tissue damage. We investigated in age matched patients the possible difference in TNF involvement in a predominantly IgA mediated disease, Henoch-Schönlein purpura (HSP), in comparison with systemic lupus erythematosus (SLE), in which vascular injury is mostly associated with local deposition of IgG immune complexes. METHODS: Serum concentrations of TNF-alpha and its soluble receptors (sTNF-R) p55 and p75 were studied in 20 patients with pediatric SLE at various degrees of disease activity, in 16 patients with highly active HSP, and in 15 healthy controls by enzyme amplified sensitivity immunoassay. SLE disease activity was evaluated using 2 scores, the European Consensus Group Study for SLE Disease Activity Criteria and the SLE Disease Activity Index. RESULTS: Serum concentrations of TNF-alpha fell within the normal range in patients with both SLE and HSP irrespective of disease activity. Conversely, patients with SLE displayed increased serum levels of sTNF-R that correlated positively with the degree of disease activity (r = 0.60, p < 0.001; r = 0.71, p < 0.001, for p55 and p75, respectively). In contrast, no difference in the serum levels of sTNF-R was found between patients with highly active HSP and controls. CONCLUSION: Our study provides the first circumstantial evidence that pediatric SLE and HSP are characterized by differential involvement of TNF in the pathogenesis of tissue damage.

Adolescent↗
PubMed1998

Growth factors increase retroviral transduction but decrease clonogenic potential of umbilical cord blood CD34+ cells.

BACKGROUND AND OBJECTIVE: The feasibility of gene marking or gene therapy protocols making use of purified CD34+ cells greatly depends on the efficiency of their stable transduction. The great potential of umbilical cord blood as a source of CD34+ cells combined with the availability of advanced cell purification procedures prompted us to evaluate whether incubation with growth factors might influence the type of cells effectively transduced by retroviral vectors. DESIGN AND METHODS: Isolated, at least 95% pure, CD34+ cells were infected with the LXSN murine retrovirus carrying the neomycin-resistance gene. Different schedules of CD34+ cell infection were performed with or without incubation for different times in the presence of Interleukin-3 (IL-3), Interleukin-6 (IL-6) and stem cell factor (SCF). Efficiency of transduction was evaluated by clonogenic assays, semiquantitative PCR and RT-PCR analyses performed either immediately or after 7 day expansion of CD34+ cells in liquid culture in the presence of erythropoietin (EPO), IL-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF). RESULTS: The results obtained indicated that the amount of transduced cells increased with the lenght of incubation with growth factors, either before or during infections. However, different types of cells were transduced depending on the duration of stimulation and infection. Thus, following one week culture of CD34+ cells in the presence of EPO, IL-3 and GM-CSF the clonogenic potential was affected dyshomogeneously. Precisely, with a single 3-hour infection performed after 12 hours of stimulation with growth factors, the clonogenic potential of the transduced cells greatly increased after one week in culture. In contrast, with a 48 hour infection, the transduced cells completely lost their clonogenic potential after one week in culture. INTERPRETATION AND CONCLUSIONS: These results demonstrate that a reasonably high transduction efficiency of purified CD34+ cells can be achieved with short schedules of incubation/infection in the absence of stroma or extracellular matrix.

Antigens, CD34↗
PubMed1997

Recombinant tumor necrosis factor enhances the locomotion of memory and naive B lymphocytes from human tonsils through the selective engagement of the type II receptor.

Recent studies performed in mice knocked out for the tumor necrosis factor (TNF ), the lymphotoxin-alpha, or the type I TNF receptor (R), genes have shown that these animals display gross defects in germinal center (GC) formation, suggesting that members of the TNF and TNFR superfamilies are involved in the control of B-cell migration. Based on these premises, we have here investigated the effects of human recombinant (r) TNF on the polarization and locomotion of tonsillar B cells. rTNF increased the spontaneous polarization and locomotion of unfractionated tonsillar B lymphocytes in a dose-dependent manner by inducing a true chemotactic response. Memory (IgD-, CD38(-)) and naive (IgD+, CD38(-)), but not GC (IgD-, CD38(+)) B cells purified from total tonsillar B lymphocytes, showed a significantly higher locomotion in the presence than in the absence of rTNF. Accordingly, type I and II TNF receptors (TNFRs) were detected by flow cytometry on the surface of memory and naive, but not GC, B lymphocytes. Blocking experiments with monoclonal antibodies to type I or II TNFR showed that rTNF enhanced the spontaneous chemotaxis of memory and naive B cells through the selective engagement of type II TNFR. Finally, the TNF gene was found to be expressed in memory, naive and GC B lymphocytes; the cytokine was released in culture supernatants from the three B-cell subsets after stimulation. These data may support the hypothesis that human TNF is involved in the paracrine and perhaps autocrine control of B-cell migration in secondary lymphoid tissues.

Animals↗