PubMed Health⌕ Search

Biomedical subjects

R Biagiotti

Publications and source records attributed to R Biagiotti.

At least 55 records · Page 3Linked to original sources
PubMed1990

A novel pathway of human B cell activation initiated by CK226 surface antigen.

In this study we analyzed the effect of CK226 monoclonal antibody (mAb) on human B cell activation and proliferation. This mAb was shown to recognize a 75-kDa surface molecule expressed on both T and B lymphocytes and to mediate T lymphocyte activation and proliferation. Flow cytometry analysis of B cell populations isolated from peripheral blood, tonsil and spleen showed that CK226 surface antigen is highly expressed on 40-80% of surface Ig+ cells. When purified B cells were cultured in the presence of CK226 mAb, up-regulation of major histocompatibility complex class II and CD23 surface structures and the de novo expression of CD25 antigen could be detected within 48 h. In addition, B cells underwent proliferation ([3H] thymidine uptake) in the absence of either T cells or exogenous lymphokines. Proliferation was potentiated by the addition of suboptimal concentrations (0.5 ng/ml) of phorbol 12-myristate 13-acetate (PMA). Cells recovered at day 5 were surface Ig+ and no CD3+ cells could be detected. CK226-induced proliferation (either in the presence or in the absence of PMA) was not inhibited by anti-CD25 mAb. Addition of exogenous interleukin 2 to CK226-stimulated B cells resulted in further increase of B cell proliferation. On the other hand, CK226 mAb did not display a co-stimulatory effect with submitogenic concentrations of either anti-Ig antibody or Staphylococcus aureus Cowan strain I bacteria. In addition proliferation induced by mitogenic concentrations of the above stimuli was inhibited in a dose-dependent fashion by CK226 mAb.

Antibodies, Anti-Idiotypic↗
PubMed1989

Analysis of the B-cell growth-promoting activity of human IL-4, the co-stimulatory assay with anti-immunoglobulin antibodies. Comparison with the B-cell growth-promoting activity of other lymphokines.

Human recombinant interleukin-4 (rIL-4) was assessed for its ability to promote the proliferative response of purified human B cells co-stimulated with submitogenic concentrations of soluble F(ab')2 fragments of anti-immunoglobulin (Ig) antibodies. The growth-promoting activity of rIL-4 was usually as potent as, or even more potent than, that of recombinant interleukin-2 (rIL-2), and more potent than that of recombinant interferon-gamma (rIFN-gamma). Preincubation with rIL-4 did not cause enhancement of the proliferative response of B cells to the subsequent addition of rIL-4 and anti-IgM antibody. In contrast, the proliferative response of B cells preincubated with anti-IgM antibody and rIL-4 was potentiated by the subsequent addition of rIL-4. The simultaneous addition of rIFN-gamma and rIL-2 or rIFN-gamma and rIL-4 had an additive effect in comparison with the response induced by rIL-2 or rIL-4 alone, respectively, whereas simultaneous addition of rIL-2 and rIL-4 induced a response equal or lower than that stimulated by rIL-2 or rIL-4 alone. The addition of rIFN-gamma at the beginning of culture or preincubation of B cells with rIFN-gamma and anti-IgM antibody potentiated the proliferative response of B cells to the subsequent addition of either rIL-2 or rIL-4. Taken together, these data suggest that rIL-4 acts as a growth factor for activated human B cells and displays on such cells a growth-promoting activity similar to that of rIL-2.

Adjuvants, Immunologic↗
PubMed1987

Role of HLA class I and class II antigens in activation and differentiation of B cells.

The monoclonal antibodies (MoAb) CR10-214, CR11-115, and Q1/28 to distinct monomorphic determinants of HLA class I antigens, the MoAb CL413 and PTF29.12 recognizing monomorphic determinants of HLA-DR antigens, the anti-HLA-DQw1 MoAb KS11, the anti-HLA-DPw1 MoAb B7/21, and the anti-HLA-DR,DP MoAb CR11-462 were tested for their ability to modulate human B-lymphocyte proliferation and maturation to IgM-forming cells. Purified tonsillar B cells were stimulated with Staphylococcus aureus bacteria of the Cowan first strain (SAC) or anti-human mu-chain xenoantibodies, as well as in growth factor- or T-cell-dependent activation cultures. The B-cell proliferative responses induced by SAC or by mitogenic concentrations of anti-mu-chain xenoantibodies were inhibited by some of the anti-HLA class I and anti-HLA class II monoclonal antibodies tested. The same antibodies were effective inhibitors of the proliferation of B cells stimulated with interferon-gamma (IFN-gamma) or interleukin-2 (IL-2) and with submitogenic concentrations of anti-mu-chain xenoantibodies. The proliferation induced by IL-2 of SAC-preactivated B cells was inhibited by some of the anti-HLA class II monoclonal antibodies, but not by the anti-HLA class I monoclonal antibodies tested. This inhibition appeared to reflect at least in part a direct effect on later events of the B-cell activation cascade, since some anti-HLA class II monoclonal antibodies still exerted considerable inhibitory activity when added together with IL-2 to SAC-preactivated B cells after the third day of culture. Anti HLA-DR, DQ, and DP monoclonal antibodies consistently inhibited the IgM production induced in B cells by T cells alone, T cells plus pokeweed mitogen (PWM), SAC plus IL-2, or IL-2 alone. In contrast, two of the three anti-HLA class I monoclonal antibodies tested inhibited the IgM production in cultures stimulated with SAC plus IL-2 and one the IgM production induced by IL-2 alone, but none of them had inhibitory effects on T-cell dependent IgM production. The results reported herein indicate that HLA class II molecules directly participate in different phases of the B-cell activation cascade. In addition, our data also suggest that HLA class I molecules can be involved in the events leading to B-cell proliferation and differentiation into immunoglobulin-secreting cells.

Antibodies, Monoclonal↗
PubMed1987

Mechanism of activation of human basophils by Staphylococcus aureus Cowan 1.

We investigated the capacity of Staphylococcus aureus Cowan 1 and S. aureus Wood 46 to induce histamine release from human basophils in vitro. S. aureus Cowan 1 (10(5) to 10(7)/ml), which synthesizes protein A (Staph A), stimulated the release of histamine from basophils, whereas S. aureus Wood 46 (10(5) to 2 X 10(7)/ml), which does not synthesize Staph A, did not induce histamine secretion. Soluble Staph A (10(-3) to 10 micrograms/ml), but not staphylococcal enterotoxin A, induced histamine secretion from human basophils. Staph A binds through its classical site to the Fc region of human immunoglobulin G (IgG) and through its alternative site to the Fab portion of the different human immunoglobulins. Hyperiodination of Staph A, which destroys over 90% of the original Fc reactivity without altering the Fab-binding site, did not alter the ability of the protein to induce histamine release. The stimulating effect of Staph A was dose dependently inhibited by preincubation with human polyclonal IgG (0.3 to 100 micrograms/ml) and a human monoclonal IgM (0.3 to 100 micrograms/ml) which have F(ab')-Staph A reactivity. In contrast, rabbit IgG, which possesses only Fc-Staph A reactivity, and a Staph A-unreactive human monoclonal IgM did not inhibit Staph A activity. Similar results were obtained with intact S. aureus Cowan 1. Preincubation with either Staph A or anti-IgE (rabbit anti-Fc epsilon) resulted in complete desensitization to a subsequent challenge with the homologous stimulus. Staph A and anti-IgE induced partial cross-densensitization to the heterologous stimulus. Cells preincubated with anti-IgG (rabbit anti-Fc gamma) lost a small but significant part of their ability to release with Staph A but did not lose their response to anti-IgE. Basophils from which IgE had been dissociated by brief exposure to lactic acid no longer released histamine in response to anti-IgE and Staph A. When basophils from which IgE had been dissociated were incubated with human polyclonal IgE, they regained their ability to induce histamine in response to Staph A and anti-IgE. In contrast, two monoclonal IgEs which do not bind to Staph A did not restore the basophil responsiveness to Staph A. Furthermore, there was complete cross-desensitization between soluble Staph A and S. aureus Cowan 1, while cells desensitized to S. aureus Wood 46 released normally with Staph A and S. aureus Cowan 1.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Analysis of the role of interferon-gamma, interleukin 2 and a third factor distinct from interferon-gamma and interleukin 2 in human B cell proliferation. Evidence that they act at different times after B cell activation.

Recombinant interferon-gamma (rIFN-gamma) was able to induce proliferation of human tonsillar B cells activated with suboptimal concentrations of anti-mu antibody. The B cell growth factor (BCGF) activity of rIFN-gamma was not due to substances contaminating the IFN-gamma preparation, nor was it mediated by factors released by T cells or large granular lymphocytes following activation by rIFN-gamma. The response of B cells to rIFN-gamma peaked on day 3 of culture and rapidly declined thereafter, whereas the response of parallel anti-mu-activated B cell cultures to recombinant interleukin 2 (rIL2) appeared on day 3, but continued at least until day 5. In addition, B cells responsive to rIFN-gamma could be at least in part separated from those responsive to rIL2, the former being primarily contained in B cell fractions enriched for high-density small B lymphocytes. Finally, the addition to anti-mu-stimulated B cell cultures of very low concentrations of rIFN-gamma potentiated the B cell proliferation promoted by rIL2. The simultaneous addition of monoclonal antibodies against IFN-gamma and T cell activation antigen to anti-mu-stimulated B cell cultures strongly reduced the B cell proliferative response promoted by three different crude BCGF preparations obtained by polyclonal T cell activation in mixed lymphocyte culture. However, the supernatant from a T cell clone (DP5/11) apparently free of IL2, which manifested a BCGF activity similar to that of rIFN-gamma, still maintained its ability to promote proliferation of anti-mu-activated B cells after complete removal of IFN-gamma. Taken together, our data indicate that although some T cell clones are able to produce a BCGF distinct from both IFN-gamma and IL2, these lymphokines account for most of the BCGF activity of supernatants obtained from polyclonal T cell populations. They also suggest that IFN-gamma and the BCGF distinct from IFN-gamma and IL2 act primarily in the earlier phases of B cell activation and potentiate the proliferative response of activated B cells to IL2.

Adjuvants, Immunologic↗
PubMed1986

HTLV-III seropositivity in symptom-free Italian haemophiliacs. Correlation with consumption of commercial concentrate and abnormalities of T and B lymphocytes.

Various immunological parameters exploring both T- and B-cell functions were determined in a group of 74 symptom-free Italian haemophiliacs treated with commercial concentrate imported from the USA and were correlated with the presence in their serum of antibody to HTLV-III. There was a strong correlation between HTLV-III seropositivity and the amount of concentrate consumed. A significant correlation between HTLV-III seropositivity and T-cell alterations, such as T4/T8 ratio less than 1 and reduction in the absolute number of T4+ lymphocytes, or B-cell alterations such as hypergammaglobulinaemia and enhanced spontaneous IgG synthesis in vitro, was also observed.

Antibodies, Viral↗
PubMed1986

Abnormalities of in vitro immunoglobulin production in apparently healthy haemophiliacs: relationship with alterations of T cell subsets and with HTLV-III seropositivity.

The pokeweed mitogen (PWM)-induced immunoglobulin (Ig) production by cultures of peripheral blood mononuclear cells (PBMC) was reduced in healthy haemophiliacs treated with commercial factor VIII (or IX) concentrate, whereas the spontaneous IgG synthesis in vitro was enhanced. PWM-induced Ig production was lower in those who had received greater amounts of concentrate, in those with inverted T4/T8 lymphocyte ratios and in those with antibody to HTLV-III. The spontaneous IgG production in vitro was higher in haemophiliacs who had received larger amounts of concentrate, in those with inverted T4/T8 ratio and in those with antibody anti-HTLV-III. However, some patients with normal T4/T8 ratio and some with HTLV-III antibody also had raised spontaneous IgG production.

Antibodies, Viral↗
PubMed1986

Direct induction of human B-cell differentiation by recombinant interleukin-2.

Recombinant interleukin-2 (rIL-2) induced highly purified human tonsillar B cells to differentiate into immunoglobulin (Ig)-producing cells in vitro. The B-cell response was not due to rIL-2-contaminating substances, but reflected the activity of IL-2 itself, since it was inhibited by addition to the cultures of anti-TAC monoclonal antibody. The rIL-2-induced B-cell response was apparently not mediated by factors released by residual T cells present in B-cell suspensions at undetectable levels, since supernatants (SN) from unstimulated autologous T cells cultured at concentrations even much higher than those possibly contaminating B-cell suspensions did not induce any detectable Ig production. In addition, the Ig production by B cells cultured with SN prepared from high numbers of autologous T cells stimulated with rIL-2, as well as from allo-activated or mitogen-stimulated T cells, was of the same magnitude as the Ig production resulting from direct addition of rIL-2 concentrations comparable with those present in the supernatants. After centrifugation on Percoll density gradients, most of the tonsillar B cells responsive to rIL-2 were recovered in the lower density cell fraction containing a number of larger activated B cells. Moreover, B-cell enriched suspensions from peripheral blood (PB) (which usually contains a lower number of in vivo activated B cells than tonsil) showed poor or no response to rIL-2 alone, but displayed significant Ig production when rIL-2 was added to the cultures in the presence of Staphylococcus aureus Cowan I (SAC) bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

B-Lymphocytes↗
PubMed1985

Different reactivity of activated human B cells to B-cell growth factor and interleukin 2 in the costimulation assay with anti-IgM antibody and in the preactivation assay with Staphylococcus bacteria.

The two main assay systems which have been developed for the study of lymphokine-mediated human B-cell proliferation, i.e., the costimulation assay with anti-mu antibody and the preactivation assay with Staphylococcus aureus Cowan I (SAC) bacteria, were compared. Purified interleukin 2 (IL-2), obtained by the recombinant DNA technology (r-IL-2), enhanced the proliferative response of anti-mu-stimulated human B cells in the costimulation assay with anti-mu antibody and maintained the B-cell proliferation induced by preactivation with SAC bacteria. Although the majority of T-cell clones, established from normal peripheral blood T lymphocytes, showed production of both IL-2 and B-cell growth factor (BCGF) following phytohemagglutinin (PHA)-stimulation, some T-cell clones were found whose supernatants (PHA-SN), apparently free of IL-2, manifested strong BCGF activity in the costimulation assay with anti-mu antibody. However, the same clonal, IL-2-free, T-cell SN displayed no BCGF activity in the preactivation assay with SAC bacteria. When B cells were activated for 3 days with anti-mu antibody, followed by the addition of r-IL-2 or clonal T-cell SN containing BCGF for an additional 3 days, r-IL-2 showed the ability to maintain B-cell proliferation, whereas clonal SN containing BCGF had virtually no effect. These data indicate that the costimulation assay with anti-mu antibody explores the reactivity of normal human B cells to both BCGF and IL-2, whereas the preactivation assay with SAC bacteria, due to a shorter reactivity to BCGF of activated human B cells, essentially represents a probe for the study of IL-2-promoted B-cell proliferation.

Antibodies, Anti-Idiotypic↗
PubMed1985

Synergy of B cell growth factor and interleukin 2 in the proliferation of activated human B cells.

The activity of purified interleukin 2 (IL2), obtained by the recombinant DNA technology, on the proliferative response of human B cells stimulated with low concentrations of anti-mu antibody was investigated. Recombinant IL2 was capable of augmenting the proliferative response of anti-mu-activated B cells and the T cell activation (Tac) antigen was expressed on a substantial proportion of normal B cells stimulated with anti-mu antibody. However, crude supernatants from protein A-stimulated peripheral blood mononuclear cells, which were found to possess both IL2 and B cell growth factor (BCGF) activities, maintained the ability to promote proliferation of anti-mu-activated B cells after depletion of IL2. In addition, supernatants from some T cell clones, apparently free of IL2 activity, displayed strong BCGF activity in the co-stimulation assay with anti-mu antibody. This BCGF activity was found in 25 kDa fractions by gel filtration and it was unaffected by addition to the cultures of anti-Tac antibody, which consistently inhibited the B cell proliferative response promoted by recombinant IL2. The proliferative response of anti-mu-activated B cells to clonal, IL2-free supernatants containing BCGF and recombinant IL2 present together from the beginning of culture was close to the sum of responses to the two stimulants, separately. In addition, the presence of clonal supernatant containing BCGF from the beginning of culture had a synergistic effect in the response of activated B cells to the subsequent addition of IL2, whereas the initial presence of IL2 had no such an effect on the reactivity of anti-mu-stimulated B cells to the late addition of clonal supernatant containing BCGF. The synergistic effect of BCGF in the IL2-promoted B cell proliferation was probably the result of the recruitment of a greater number of IL2-reactive B cells. In fact, the number of Tac-positive cells was significantly higher in 36-h cultures established in the presence of anti-mu antibody plus clonal supernatant containing BCGF than in cultures stimulated with anti-mu antibody alone. Taken together, these data indicate that anti-mu antibody promotes the expression by normal human B cells of distinct receptors for IL2 and a BCGF distinct from IL2. They also suggest that BCGF can exert a synergistic effect in the IL2-promoted proliferation of activated B cells.

Antibodies, Anti-Idiotypic↗
PubMed1985

Activation of human basophils by Staphylococcus aureus Cowan I. II. Alternative F(ab')-mediated mechanism.

We investigated the capacity of Staphylococcus aureus Cowan I (Cowan Staph A+) and Staphylococcus aureus Wood 46 (Wood Staph A-) to induce histamine release from human basophils in vitro. Cowan Staph A+ (3 X 10(6) to 3 X 10(8)/ml), which synthesizes protein A (Staph A), stimulated the release of histamine from basophils, whereas Wood Staph A- (3 X 10(6) to 3 X 10(9)/ml), which does not synthesize Staph A, did not induce histamine secretion. Soluble Staph A (10(-3) to 10 micrograms/ml) also induced histamine secretion from human basophils, Hyperiodination of Staph A, which destroys over 90% of the original Fc reactivity without altering the Fab binding site, did not alter this protein's ability to induce histamine release. The stimulating effect of Staph A was suppressed by preincubation with human polyclonal IgG and a human monoclonal IgM, which have F(ab')-Staph A reactivity. In contrast, rabbit IgG and a human monoclonal IgM possessing only Fc-Staph A reactivity did not inhibit Staph A activity. Preincubation with Staph A or Cowan Staph A+ resulted in complete cross-desensitization to a subsequent challenge with homologous and heterologous stimuli. These results indicate that Staph A and Cowan Staph A+ activate human basophils by interacting with the F(ab')2 region of IgE and/or IgG present on the cell surface.

Basophils↗
PubMed1985

Role of class II histocompatibility antigens in Staphylococcus aureus protein A-induced activation of human T lymphocytes.

The capacity of peripheral blood monocytes and B lymphocytes to support staphylococcal protein A (SpA)-induced proliferation of autologous and allogeneic T cells, as well as the role of major histocompatibility complex (MHC) class I and II molecules in this activation process, were investigated. Highly purified peripheral T lymphocytes did not proliferate in response to SpA, but their response was reconstituted by both irradiated (or mitomycin C-treated) monocytes and B lymphocytes. The effect of B cells on the SpA-induced T-cell response could not be explained by a contamination of residual accessory cells because long-term continuous B-cell lines restored SpA-induced T-cell DNA synthesis as effectively as did monocytes. Support of SpA responsiveness by B cells could not be accounted for by polyclonal binding of SpA to cell surface immunoglobulins, since the ability of SpA-unreactive and SpA-reactive B cells was comparable. The cells from two human leukemic lines--K562 and Raji--showed the same ability in supporting the pokeweed mitogen-induced T-cell response, but the class II-positive Raji cells were much more effective than class II-negative K562 cells in restoring the T-cell responsiveness to SpA. Monoclonal antibodies specific for monomorphic determinants of MHC class II antigens, as well as their F(ab')2 fragments, consistently inhibited the SpA-induced proliferative response, whereas antibodies specific for MHC class I antigens were without effect. The antibodies specific for class II antigens appeared to act at the level of accessory cell, since pretreatment with these antibodies inhibited the ability of SpA-pulsed monocytes or Raji cells to present SpA to autologous or allogeneic T lymphocytes, respectively. These data indicate that either monocytes or normal and lymphoblastoid B cells can act as accessory cells for the proliferative response of human T cells to soluble SpA and that monomorphic determinants of MHC class II molecules play an important role in this activation process.

Histocompatibility Antigens↗
PubMed1985

Anti-Ia reactivity in sera of untreated patients with active Hodgkin's disease.

The effect of sera from eight patients with Hodgkin's disease on the autologous and allogeneic mixed lymphocyte response of normal individuals was examined. Sera from three patients with active disease caused marked inhibition of both autologous and allogeneic mixed lymphocyte reaction without inducing significant reduction of the phytohemagglutinin-induced proliferative response. The inhibitory activity of Hodgkin's disease sera on the autologous mixed lymphocyte reaction was removed by adsorption with non-T, but not T, lymphocytes and it was correlated with the ability of such sera to block the binding of monoclonal anti-Ia antibody to Ia-positive target cells. Anti-Ia antibodies were detected in the same sera by double antibody radioimmunoassay and analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, using 125I-labeled, partially purified, Ia antigens from two different human B-cell lines. This anti-Ia reactivity was strongly reduced or absent in sera taken from the same patients at the completion of multidrug chemotherapy.

Antibodies↗
PubMed1982

Protein A reactivity of lymphocytes from some patients with chronic lymphocytic leukaemia mediated by an interaction with the F(ab')2 region of surface immunoglobulin.

Peripheral blood lymphocytes (PBL) from 15 of 38 patients with chronic lymphocytic leukaemia (CLL) were capable of forming rosettes with human erythrocytes coated with staphylococcal protein A (SpA-HRBC). PBL from seven patients also showed a marked proliferative response after stimulation with Staphylococcus aureus bacteria strain Cowan I (Cowan Staph). The SpA-rosetting of CLL cells was inhibited by incubation with F(ab')2 fragments of anti-immunoglobulin (Ig) antibodies. In addition, incubation with these fragments inhibited the proliferative response of leukaemic B cells to Cowan Staph. The Cowan-Staph induced proliferation of CLL cells was also impaired by the addition of normal human IgG and human IgG F(ab')2 fragments to the cultures, whereas non-immune rabbit IgG was not inhibitory. The inhibitory activity of human IgG F(ab')2 fragments was retained by a SpA-Sepharose column, and it was found in the material recovered from the same column by acid elution. These data indicate that an interaction between SpA and a structure located in the F(ab')2 region of surface Ig of different classes is responsible for either SpA-binding or the Cowan-Staph-induced proliferative response of PBL from some patients with CLL.

Animals↗
PubMed1982

In vitro production of IgE by human peripheral blood mononuclear cells. III. Demonstration of a circulating IgE-bearing cell involved in the spontaneous IgE biosynthesis.

The presence of surface membrane IgE (SmIgE)-bearing cells in the peripheral blood (PB) of atopic patients was investigated by the use of isotype-specific rosettes of human red blood cells coupled to immunosorbent-purified rabbit or monoclonal mouse antibodies against human IgE (R or M anti-epsilon-HRBC). After dissociation of cell bound IgE by treatment with acid buffer, 2.1 +/- 0.3% and 1.2 +/- 0.3% circulating non-T, non-phagocytic, cells from atopic patients were still capable of forming rosettes with R or M anti-epsilon-HRBC, respectively. IgE molecules detectable on cells after dissociation of cytophilic IgE were quite resistant, like surface membrane IgM (SmIgM), to treatment with proteolytic enzymes, but they were removed under capping conditions by soluble anti-IgE antisera. All SmIgE-bearing (IgE+) cells also bore DR determinants, but many of them lacked SmIgM. Depletion of IgE+ cells strongly reduced the ability of PB lymphocyte suspensions from atopic patients to produce spontaneously IgE protein in vitro. Likewise, depletion of cells bearing DR determinants (DR+ cells) resulted in a marked decrease of the spontaneous IgE biosynthesis, whereas depletion of SmIgM-bearing (IgM+) cells had no effect. These data suggest that cells mainly implicated in the spontaneous IgE production in vitro seen in atopic patients are DR+ IgE+ IgM- circulating lymphocytes.

Antibodies, Monoclonal↗