[Retrospective analysis of diagnosis and treatment of breast cancer in pregnancy].

Objective: To investigate the principles of diagnosis and treatment of breast cancer during pregnancy. Methods: Clinical data of patients with breast cancer during pregnancy admitted to Obstetrics and Gynecology Hospital of Fudan University between January 2012 to July 2017 were analyzed retrospectively. A total of 17 patients were diagnosed with breast cancer in pregnancy, the median age was 32 years (range from 25 to 45 years old), pathological staging revealed 2 patient with stage 0, 1 with stage Ⅱa, 7 with stage Ⅱb, 1 with stage Ⅲa, 2 with stage Ⅲc, 4 with stage Ⅳ. Results: Thirteen patients received surgical treatment in pregnancy, the gestational age at surgery was (27.7±4.6) weeks; 2 patients with ductal carcinoma in situ received mastectomy, 11 patients with breast cancer underwent modified radical mastectomy. In patients undergoing surgery during pregnancy, no prophylactic contractions were used in 4 patients who had been treated earlier, there were 2 patients with frequent contractions within 24 hours after operation in these patients. Follow-up 9 patients were given oral nifedipine to prevent contractions, no obvious contractions occurred after the operation. Seven patients received chemotherapy during pregnancy; the chemotherapy of 4 cases of triple negative breast cancer was weekly paclitaxel sequential epirubicin and cyclophosphamide, the chemotherapy of the other three patients was docetaxel sequential epirubicin and cyclophosphamide. Fifteen patients underwent cesarean section to terminate pregnancy, 2 patients underwent spontaneous labor. The gestational age of birth was (36.9 ±1.3) weeks. Less than 35 weeks of termination of pregnancy occurred in one patient, the fetus was delivered to the neonatal intensive care unit due to neonatal respiratory distress syndrome, and suffered from congenital dysaudia. The prognosis of the other 16 survived infants was good. The median follow-up time was 10 months (range from 4 to 27) months, in 13 patients of stage 0 to Ⅲc, one patient were diagnosed with bone metastasis at 12 months after surgery, the remaining 12 patients had no disease progression, the progression free survival rate was 12/13, the overall survival rate was 13/13. Among the 4 patients with stage Ⅳ, one died in 7 months after delivery, one had new liver metastasis in 8 months after delivery. The remaining 2 patients were in stable condition. Conclusions: Breast cancer in pregnancy can be treated effectively, multidisciplinary cooperation and detailed assessment of maternal-fetal risks and benefits are necessary. Chemotherapy during pregnancy is safe for maternal-fetal, but it needed a large sample of clinical studies and long-term follow-up. The neonatal outcome was associated with gestational age, and therefore premature delivery was avoided as much as possible during treatment.

G12V Kras mutations in cervical cancer under virtual microscope of molecular dynamics simulations.

Kras mutations and cancers are common and their role in the progression of cancer is well known and elucidated. The present work is searching for the most deleterious mutation of the four found at codon 12 and 13 of Kras in cervical cancers using prediction servers; different servers were used to look into different factors that govern the protein function. The in silico results predicted G12V to be the most devastating; this particular mutation was then subjected to molecular dynamics simulation (MDS) for further analysis. The authors' approach of MDSs helped them to place the native and mutant structure under virtual microscope and observe their dynamics over time. The results generated are enlightening the effect of G12V variation on the dynamics of Kras. The structural variation between the native and mutant Kras over 50 nanoseconds (ns) run varied at every parameter checked and the results are in excellent agreement with the available experimental data.

Induction function of siRNA-mediated survivin gene silencing on nasopharyngeal carcinoma cell apoptosis.

We examined the function of survivin gene expression in patients with nasopharyngeal carcinoma (NPC), as well as small interfering RNA (siRNA) on controlling CNE-2 NPC proliferation and apoptosis. Immunohistological methods, in situ hybridization, and reverse transcription-polymerase chain reaction technique were used to detect survivin protein and mRNA expression. We designed an siRNA sequence to inhibit survivin gene expression. The MTT method was used to examine the function of siRNA on controlling cell growth and proliferation. Induction of cell apoptosis by siRNA was examined by flow cytometry; electron microscopy was used to observe ultrastructure changes in CNE-2 cells. Western blotting was used to detect survivin gene expression. The survivin protein was expressed in 71.9% of cells, while its mRNA was expressed in 65.6% of cells. Relative mRNA expression was 4.16 x 10(-2); these data for the control groups were 23.3, 33.3, and 4.42 x 10(-4), respectively. Following transfection with 3 different siRNA sequences, survivin mRNA expression in CNE-2 cells was decreased. Inhibition of cell proliferation and rate of apoptosis increased with increasing siRNA concentration. Western blotting revealed decreased survivin expression and electron microscopy revealed ultrastructural changes in cancer cells. Survivin gene expression in NPC generally increased. In vitro transcription of siRNA decreased CNE-2 survivin gene expression, and different sequences of siRNA decrease gene expression in CNE-2 cells to varying degrees. Transfected siRNA3 can effectively inhibit CNE-2 cell proliferation and induce apoptosis; gene silencing using siRNA may represent a new treatment for NPC.

Ultrastructural Changes and Putative Phage Particles Observed in Sweet Orange Leaves Infected with 'Candidatus Liberibacter asiaticus'.

Huanglongbing (HLB), also known as citrus greening, is currently the most destructive citrus disease. Anatomical analyses of HLB-affected sweet orange were carried out by light and electron microscopy. As compared with healthy citrus, the phloem plasmodesmata were plugged with callose, and in some samples the phloem was collapsed. Chloroplast structures were deformed. Prophage sequences occupy a significant portion of the genome of 'Candidatus Liberibacter asiaticus' and have been used to distinguish strains from Yunnan and Guangdong provinces in China and Florida. Interestingly, a large number of possible putative phage particles were observed attached on the surface of 'Ca. L. asiaticus' cells in plants inoculated with strain FJ3 from Fujian Province, China. Phage particles have been observed previously only in periwinkle plants artificially inoculated in Florida with 'Ca. L. asiaticus' that carried the SC1-type prophage. PCR assays verified the presence of the SC1-type prophage sequences previously described from this bacterium in Florida in the FJ3 isolate. This is the first time that suspected phage particles have been observed in sweet orange trees infected with 'Ca. L. asiaticus.'

Association of cyclin D1 and survivin expression with sensitivity to radiotherapy in patients with nasopharyngeal carcinoma.

The association between cyclin D1 and survivin protein expressions with radiotherapy sensitivity in patients with nasopharyngeal carcinoma was investigated. Biopsy specimens of 72 patients with nasopharyngeal carcinoma were collected before the initiation of radiotherapy (49 cases were in the radiation-sensitive group and 23 cases were in the radiation-insensitive group). Conventional hematoxylin and eosin staining was used for tissue typing. The immunohistochemical SP method was used to detect cyclin D1 and survivin protein expression levels. The IBM SPSS Statistics 20 statistical software was applied for conducting the chi-squared test and the Spearman correlation analysis. In the 72 cases, the high expression rates of cyclin D1 were 28.6% (14/49) and 69.6% (16/23) in the radiotherapy-sensitive group and in the radiotherapy-insensitive group, respectively, and the differences between groups were statistically significant (P<0.05). The high expression rates of survivin were 34.7% (17/49) and 73.9% (17/23) in the radiotherapy-sensitive group and in the radiotherapy-insensitive group, respectively, which differed significantly (P<0.05). The protein expressions of cyclin D1 and survivin were positively correlated (Spearman's r=0.353, P<0.05). Cyclin D1 and survivin expression levels were negatively correlated with the radiosensitivity of nasopharyngeal carcinoma. Cyclin D1 and survivin may be used as molecular markers to predict the sensitivity of radiotherapy.

Human T cell activation. I. Monocyte-independent activation and proliferation induced by anti-T3 monoclonal antibodies in the presence of tumor promoter 12-o-tetradecanoyl phorbol-13 acetate.

Three monoclonal antibodies (mAb), of IgG1, IgG2a, and IgM isotypes, raised against the T3 complex, were used to probe the activation of human T cells. The IgM antibody 235 was not mitogenic for peripheral blood mononuclear cells (PMC). It efficiently blocked the proliferation of PMC induced by T cell mitogens, alloantigens, and soluble antigens. The other two antibodies were mitogenic, and behaved similarly to Leu 4 and OKT3, respectively. In T cell preparations with less than 0.1% monocytes (as assayed by nonspecific esterase staining), all three mAb were not mitogenic. They failed to induce either interleukin 2 (IL-2) receptor expression or IL-2 secretion. Addition of IL-1 failed to collaborate with anti-T3 mAb to induce these T cells to proliferate, but IL-2 enhanced T cell proliferation slightly. Monocyte-depleted T cells, however, proliferated in response to all three anti-T3 mAb, when TPA was added, in a dose-dependent manner. TPA induced a low level of IL-2 receptor expression in monocyte-depleted T cells, without inducing IL-2 secretion. Anti-T3 plus TPA induced a marked enhancement in both quantity and intensity of IL-2 receptor expression. IL-2 secretion was also detected. These results indicate that anti-T3 IgM can deliver an inductive signal despite its blockage of T cell proliferation, and that two signals are necessary and perhaps sufficient to induce human T cell activation and proliferation.

Autoantibodies to neurofibrillary tangles and brain tissue in Alzheimer's disease. Establishment of Epstein-Barr virus-transformed antibody-producing cell lines.

Multiple EBV-transformed B cell lines were established from five patients with a clinical diagnosis of Alzheimer's disease (AD) and six age-matched controls. The supernatants were screened for antibody activity against SDS-treated isolated neurofibrillary tangles (NFT). Reactive supernatants were identified from both the AD and control group. The frequencies of anti-NFT antibody-secreting lines were 6.3 and 1.6% for the AD and the control groups, respectively. A proportion of these supernatants also stained NFT in situ and neurons and/or glia in sections of the frontal and the temporal cortexes of autopsied AD and normal brains, as well as cells from three cell lines (HeLa, fibroblast, and neuroblastoma). Several patterns of staining were revealed by these supernatants, indicating different reactive antigens. One supernatant stained NFT and astrocytes in sections from AD brains. It did not stain sections from two normal brains. This cell line is the result of the immortalization of a circulating B cell making antibody specific for an antigen in AD. The present approach may provide new insights in the pathogenesis of AD.

Detection and functional studies of p60-65 (Tac antigen) on activated human B cells.

A monoclonal antibody, AT-1, is shown to precipitate a p60-65 molecule identical to the Tac antigen. With AT-1, the expression of IL-2 receptors by normal activated human B cells from peripheral blood and tonsils is documented by biosynthetic and immunofluorescence studies. AT-1 precipitated a p60-65 protein from [35S]methionine-labeled activated B cells, similar to that from activated T cells. The interleukin 2 (IL-2) receptor appeared shortly after activation with anti-IgM and B cell-stimulatory factor(s). Its expression reached its peak at 60-72 h with approximately 50% of the B blasts stained by AT-1. Other modes of activation of B cells, by T cell-independent, formalin-treated staphylococci and Epstein-Barr virus, and by T cell-dependent pokeweed mitogen, also induced IL-2 receptor expression. The functional significance of this finding was investigated using recombinant IL-2 (rIL-2). While rIL-2 did not induce resting B cells to proliferate in the presence of anti-IgM, it induced activated B cells to proliferate in the absence of other factors. On the other hand, rIL-2 did not induce the differentiation of these activated B lymphocytes. These data suggest that IL-2 may play a significant role in B cell activation.

Induction of polyclonal antibody synthesis by human allogeneic and autologous helper factors.

Human helper factors were obtained from supernates of 48 h unidirectional allogeneic and autologous mixed lymphocyte reactions. These supernates were shown to induce the production of large amounts of immunoglobulin by tonsillar and peripheral blood mononuclear cells. Abundant polyclonal activation to antibody production occurred in these cultures in the absence of antigenic challenge which was similar in degree to that produced by pokeweed mitogen. This was documented by quantitating plasma cells, specific plaque-forming cells, and secreted immunoglobulin. In addition, the supplementation of companion cultures with sheep erythrocytes resulted in a significant enhancement of the specific plaque-forming cell response without an appreciable change in plasma cell number of secreted Ig.

Selective inhibition of growth factor-dependent human B cell proliferation by monoclonal antibody AB1 to an antigen expressed by activated B cells.

A monoclonal antibody, AB1, was established with activated human B cells as immunogen. AB1 stained activated B cells but not activated T cells. Its selective reactivity to activated B cells was further documented by its nonreactivity to activated T cells, resting T and B cells, monocytes, granulocytes, bone marrow cells, leukemic cells, and cells from cell lines of T, B, and myeloid lineages. Upon activation, the antigen appeared on B cells as early as 3-4 h after stimulation and was fully expressed by 38 h. The expression of this antigen was not dependent on the presence of B cell stimulatory factor(s). Anti-IgM antibodies by themselves induced its expression. AB1 inhibited B cell proliferation that was induced by a low dose anti-IgM antibody and conditioned medium containing B cell stimulatory factor. It did not inhibit B cell proliferation induced by either high doses of anti-IgM antibodies or by formalinized Staphylococcus aureus. It also failed to inhibit T cell mitogenesis. The possibility exists that this antigen is related to the receptor for B cell stimulatory factor.

Human T cell hybridomas secreting factors for IgA-specific help, polyclonal B cell activation, and B cell proliferation.

Human T-T hybridomas were established by fusion of concanavalin A-activated OKT-4+ T cells with hypoxanthine guanine phosphoribosyl transferase-deficient as well as nondeficient T cell lines. Four hybrids were selected for further study. Supernatant from hybrid clone J1.3 specifically enhanced IgA production and secretion by isolated human B cells, with increases in IgA plaque-forming cells approaching those seen with addition of autologous T cells and pokeweed mitogen. A monoclonal lymphocytic leukemia with membrane IgA also differentiated to IgA plasma cells by this supernatant. Evidence suggests that this hybrid supernatant acts on post-switch IgA-committed B cells. The other hybrids were not isotype specific; hybrid J2S1 enhanced polyclonal Ig secretion and hybrids K1 and K8 induced B cell proliferation without induction of Ig secretion.

Membrane immunoglobulins of B lymphocytes: inability to detect certain characteristic IgM and IgD antigens.

Hemagglutination and fluorescent antibody studies have provided strong evidence for the unavailability or absence of specific antigenic sites on membrane-bound IgM which are present in serum and intracellular IgM. Antisera specific for different parts of the molecule indicated that a portion but not all of the Fc was involved. Absorption experiments with normal and leukemic viable B lymphocytes failed to remove a population of Fc antibodies found in IgM-specific antisera. Similar findings were made for IgD, the other major membrane immunoglobulin of human peripheral blood B cells. Various interpretations of these observations are discussed. The most likely possibility appears that the C-terminal portion of the heavy chains of the immunoglobulin molecule is buried in the membrane.

Human T cell activation. II. A new activation pathway used by a major T cell population via a disulfide-bonded dimer of a 44 kilodalton polypeptide (9.3 antigen).

In previous studies (17-21), monoclonal antibody (mAb) 9.3 has been shown to react with a major population of human T cells, which include T4+ helper/inducer T cells and T8+ cytotoxic T cells. In this investigation, mAb 9.3 was shown to precipitate a disulfide-bonded dimer of a 44 kD polypeptide. Comodulation experiments showed that this molecule is not linked to T3/Ti or T11 antigens. mAb 9.3 was capable of inducing T cell proliferation in the presence of 12-o-tetradecanoyl phorbol-13-acetate (TPA). This effect was monocyte-independent. T cell activation with mAb 9.3 and TPA was associated with increases in interleukin 2(IL-2) receptor expression and IL-2 secretion. mAb 9.3 did not activate T cells, even with the addition of IL-1 or IL-2. Modulation of the T3 complex did not abolish mAb 9.3-induced T cell proliferation in the presence of TPA. These results suggest that the 9.3 antigen may serve as a receptor for an activation pathway restricted to a T cell subset.

Human antibodies reactive with beta-amyloid protein in Alzheimer's disease.

Four human B cell lines established by Epstein-Barr viral transformation of B cells from a patient with a clinical diagnosis of Alzheimer's disease (AD) were found to secrete antibodies that react with plaques and cerebrovascular blood vessels in AD brain in a staining profile characteristic of beta-amyloid protein (beta-AP) in AD brain. Two of these antibodies were shown to be reactive with a rare plaque in a normal brain. In these studies, immunofluorescence and avidin-biotin complex immunoperoxidase methodology were used to determine antibody reaction, and thioflavine S was used to double label amyloid and neurofibrillary tangles. The four antibodies also reacted with neurons in normal and AD brain. Absorption studies, dot immunoblots, and enzyme-linked immunosorbent assays with beta-amyloid peptides 1-28 (beta-A1-28) and 1-40 (beta-A1-40) indicate the major determinant of the reactive epitope is located in the region of amino acids 1-28 of beta-AP. However, inhibition studies demonstrate a significant contribution to the antigenic determinant by the 29-40 region of the beta-A1-40. These antibodies represent the first human autoantibodies against beta-AP. The pathological significance of these autoantibodies is discussed.

Human T cell activation. IV. T cell activation and proliferation via the early activation antigen EA 1.

A new mAb G38 was generated against purified EA 1, an early activation antigen. In immunoprecipitation, it was reactive with the same complex precipitated by the initial anti-EA 1 mAb P8. mAb G38 augmented PMA-induced proliferation of PBMC. It was shown to be mitogenic for purified T cells in collaboration with PMA in a dose-dependent manner. This effect was independent of monocytes and other accessory cells. mAb G38 augmented PMA-induced IL-2-R expression. In conjunction with PMA, it induced IL-2 synthesis and secretion. Its effects on IL-2-R and IL-2 expression were documented at both protein and mRNA levels. Both anti-EA 1 mAbs did not induce Ca2+ influx by themselves in PMA-treated T cells. However, the addition of second anti-mouse Ig antibodies induced readily detectable increases in [Ca2+]i. Ca2+-mediated pathways may be utilized as the transduction signal mechanisms. mAb Leu-23 was shown to be reactive with EA 1. mAb Leu-23 was also mitogenic for T cells in the presence of PMA. These findings provide evidence for a functional role for EA 1 in T cell activation and proliferation.

Human T cell activation. III. Rapid induction of a phosphorylated 28 kD/32 kD disulfide-linked early activation antigen (EA 1) by 12-o-tetradecanoyl phorbol-13-acetate, mitogens, and antigens.

With human T cells activated by 12-o-tetradecanoyl phorbol-13-acetate (TPA) as immunogen, an IgG2a mAb, early activation antigen 1 (EA 1), was generated against a 60-kD protein with disulfide-linked 28-kD and 32-kD subunits. Both subunits were phosphorylated. The antigen, EA 1, was readily detected on approximately 60% of isolated and cryopreserved thymocytes, as determined by indirect immunofluorescence. A low level of EA 1 expression was detectable on 6-7% of blood lymphocytes. TPA-activated T cells expressed EA 1 as early as 30 min after activation. By 1 h, 85-90% of the T cells stained with mAb EA 1. By 3-4 h, the expression of EA 1 was detected in greater than 95% of the T cells. Although the percentages of EA 1+ T cells did not change, the intensity of staining increased slightly. After 18-24 h, both the percentage of EA 1+ cells and the intensity of staining decreased gradually. TPA-induced EA 1 expression was independent of monocytes. EA 1 expression was slightly delayed in T cells that were isolated without the rosette selection and treated with TPA. Nevertheless, greater than 85% of these T cells expressed EA 1 within 1 h, and the maximal number of EA 1+ T cells was also detected at 3-4 h. In T cell populations with 1-2% monocytes, about 50-90% of the PHA- or Con A-activated T cells expressed EA 1 with a slower kinetics. EA 1 expression preceded that of IL-2-R in these activation processes. Similarly, T cells activated by soluble antigens (tetanus toxoid and PPD) and alloantigens in MLR also expressed EA 1 after a longer incubation. Approximately 20% of the T cells stained for EA 1 at day 6. EA 1 expression was not limited to activated T cells. B cells activated by TPA or anti-IgM antibody plus B cell growth factor expressed EA 1. The kinetics of EA 1 expression was markedly slower and the staining was less intense. Repeated attempts to detect EA 1 on resting and TPA-activated monocytes and granulocytes have not been successful. However, the detection of EA 1 in nonlymphoid cell lines would indicate that EA 1 may have a broader cell distribution. EA 1 expression was due to de novo synthesis, as the induction of EA 1 was blocked by cycloheximide and actinomycin D.(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulation of tumor necrosis factor alpha production in human monocytes by inhibitors of protein phosphatase 1 and 2A.

The protein phosphatase 1 and 2A inhibitor, okadaic acid, has been shown to stimulate many cellular functions by increasing the phosphorylation state of phosphoproteins. In human monocytes, okadaic acid by itself stimulates tumor necrosis factor alpha (TNF-alpha) mRNA accumulation and TNF-alpha synthesis. Calyculin A, a more potent inhibitor of phosphatase 1, has similar effects. TNF-alpha mRNA accumulation in okadaic acid-treated monocytes is due to increased TNF-alpha mRNA stability and transcription rate. The increase in TNF-alpha mRNA stability is more remarkable in okadaic acid-treated monocytes than the mRNA stability of other cytokines, such as interleukin 1 alpha (IL-1 alpha), IL-1 beta, and IL-6. Gel retardation studies show the stimulation of AP-1, AP-2, and NF-kappa B binding activities in okadaic acid-stimulated monocytes. This increase may correlate with the increase in TNF-alpha mRNA transcription rate. In addition to the stimulation of TNF-alpha secretion by monocytes, okadaic acid appears to modulate TNF-alpha precursor processing, as indicated by a marked increase in the cell-associated 26-kD precursor. These results suggest that active basal phosphorylation/dephosphorylation occurs in monocytes, and that protein phosphatase 1 or 2A is important in regulating TNF-alpha gene transcription, translation, and posttranslational modification.

Isolation and immunological characterization of a major surface glycoprotein (gp54) preferentially expressed on certain human B cells.

A major membrane glycoprotein with mol wt of approximately 54,000 has been isolated from membrane preparations of B-type lymphoid cell lines. Antiserum prepared against the isolated material specifically precipitated this glycoprotein from membranes labeled by surface radioiodination or by metabolic labeling. This antiserum was shown by complement-mediated cytotoxicity assay, membrane immunofluorescent staining, and by quantitative absorption analysis to react preferentially with certain B-lymphoblastoid cell lines, with a minor population of peripheral blood B lymphocytes, and a major population of tonsillar B lymphocytes. Certain B-cell leukemias also expressed the antigen, whereas others did not. Considerable variability was observed among positive B cells in the intensity of fluorescent staining even among the leukemic cells from a single individual. Although T cells, including T cells, were negative by direct immunofluorescent and cytotoxicity assay, evidence for low levels of the antigen on the cells of T cell lines was obtained. The whole specific antiserum and its F(ab')2 fragments stimulated B lymphocytes to proliferate. This proliferation did not produce differentiation to plasma cells and was T-cell independent. The monovalent Fab fragments had no effect. None of these preparations timulated T cells. The possibility that this antigen, termed gp54, may play some role in B-cell activation is discussed.

Signal transduction via CD40 involves activation of lyn kinase and phosphatidylinositol-3-kinase, and phosphorylation of phospholipase C gamma 2.

CD40 is a 50-kD glycoprotein that plays an important role in B cell survival, memory, and immunoglobulin isotype switch. Engagement of the CD40 antigen by monoclonal antibodies (mAbs) results in increased protein tyrosine kinase (PTK) activity, which plays an important role in mediating the biologic effects of CD40. We demonstrate, using an in situ phosphorylation technique, that CD40 cross-linking by the anti-CD40 mAb 626.1 resulted within 1 min in increased phosphorylation of the src type kinase, lyn, in Daudi B cell lines and remained sustained for up to 20 min. The activity of lyn kinase, as measured by immune complex kinase assay, was also increased after CD40 engagement, with similar kinetics. In contrast, the phosphorylation and activity of fyn, fgr, and lck kinases demonstrated minimal changes following stimulation of Daudi cells with mAb 626.1 over this same time period. CD40 engagement also resulted in phosphorylation of phospholipase C gamma 2 of phosphatidylinositol (PLC gamma 2) and phosphatidylinositol (PI)-3-kinase. Phosphorylation of PI-3-kinase was shown to be associated with an increase in its enzymatic activity. These results suggest that lyn plays an important role in CD40-mediated PTK activation and identify PLC gamma 2 and PI-3-kinase targets for CD40-mediated phosphorylation, suggesting a role for these two enzymes in CD40 signal transduction.

CD40 signaling pathway: anti-CD40 monoclonal antibody induces rapid dephosphorylation and phosphorylation of tyrosine-phosphorylated proteins including protein tyrosine kinase Lyn, Fyn, and Syk and the appearance of a 28-kD tyrosine phosphorylated protein.

CD40 plays an important role in B cell activation, proliferation, and Ig class switching. The signal transduction pathway mediated by CD40 was studied using monoclonal antibody (mAb) 626.1 to CD40. Burkitt's lymphoma and Epstein-Barr virus-transformed B cell lines and tonsilar B lymphocytes were treated with the anti-CD40 mAb for various lengths of time. The early events triggered by CD40 were examined by monitoring the changes in tyrosine phosphorylation of cellular proteins with anti-phosphotyrosine mAb. Dephosphorylation of specific proteins ranging between 50-110 kD and the appearance of a 28-kD tyrosine phosphorylated protein were seen within 30 s in human B cell lines. The dephosphorylation was reversed and the 28-kD protein was dephosphorylated in cells stimulated for 1 min. In resting B cells, the appearance of the 28-kD phosphoprotein was observed in 30 s after the addition of the anti-CD40 mAb. The tyrosine phosphorylation of this protein persisted. The patterns of protein tyrosine phosphorylation differed from those induced by an anti-immunoglobulin M mAb. The changes in the state of tyrosine phosphorylation induced by the anti-CD40 mAb were obviated by mAb to CD45, a protein tyrosine phosphatase (PTP) or by the addition of sodium orthovanadate, a broad PTP inhibitor. They were also blocked by protein tyrosine kinase (PTK) inhibitors, herbimycin A and genistein, and PKC and protein serine/threonine kinase inhibitors, H7 and HA1004. In addition, the alteration in the tyrosine phosphorylation of PTKs Lyn, Fyn, and Syk was directly demonstrated. Engagement of CD40 for 30 s induced a transient decrease in tyrosine phosphorylation of these PTKs. These results indicate that the early events in CD40 signaling involve the complex interaction between PTP and protein kinases.