Search

Stimulation of the neural cell adhesion molecule (NCAM) by homophilic interactions is known to lead to neurite outgrowth as well as to neuronal survival. Whereas a complex network of signalling molecules is known to be of importance to NCAM-mediated neurite extension, only limited information is available regarding signalling underlying NCAM-mediated neuroprotection. Here, we present data suggesting a difference in the signalling events required for survival of rat dopaminergic neurons as compared with neurite outgrowth from the same cell type. Whereas Fyn, fibroblast growth factor receptor, mitogen-activated protein and ERK kinase, protein kinase A and protein kinase C are required for both responses to NCAM-induced signalling, phospholipase C and Ca(2+)-calmodulin-dependent kinase II are only necessary for the neurite outgrowth response, but dispensable for neuroprotection.

To explore modulation of the molecular adjuvant C3d in the hCGbeta -C3d3 fusion protein in costimulatory molecule expression on Raji cells by linking to the surface molecule CD21. Raji cells, B cell line, were incubated with the purified hCGbeta-C3d3, hCGbeta or C3d3 protein for 15 hours respectively in the interference of anti-CD21 monoclonal antibody or not. The culture concentration of each group was 10, 30, or 90 microg/ml respectively. The expression of both B7-1 and B7-2 on Raji cells were analyzed by flow cytometric assay. It was observed that compared to hCGbeta or C3d3 protein, hCGbeta-C3d3 up-regulated both B7-1 and B7-2 expression on the Raji cells, and the effect was in a dose-dependent manner. The up-regulation effect was blocked efficiently by anti-CD21 mAb. The results showed that molecular adjuvant C3d may up-regulate both B7-1 and B7-2 expression on Raji cell via C3d/CD21/CD19 complex, thus enhance the antigen presentation of B cell, and the interaction between B cell and T cell.

Co-cultures of entorhinal cortex (EC) and dentate gyrus (DG) explants are a useful model system to study the formation and stabilization of axonal projections. We adapted this model system to EC-DG co-cultures on microelectrode arrays (MEA) for the characterization of axonal projections on a functional level for days and weeks. EC and DG explants were placed on MEA to allow for the reconstitution of perforant pathway projections. Connections formed were characterized by morphological and electrophysiological analyses to verify characteristic features of perforant pathway signal transmission. Morphological analysis reveals proper projection of EC neurons into the molecular layer of the DG. Examination of synaptic transmission after high frequency stimulation imply unidirectional connections that used glutamate receptors of the AMPA/kainate type as main mediators of excitatory signal transmission. The system was evaluated by the introduction of the NCAM binding peptide C3d. In accordance with in vivo and in vitro experiments C3d modulated signal transmission by NCAM-related mechanisms resulting in morphological re-arrangements.

Objective: To testify the effect of C3d molecular adjuvant on the immunogenicity of human chorionic gonadotropin beta (hCG beta) DNA vaccination as well as the mode of immune response., Methods: BALB/c mice aged 6 weeks were immunized intramuscularly two times at an interval of 3 weeks with by the plasmid pcDNA3 (A1-3 groups), pcDNA3-hCG beta (B-3 groups), pcDNA3-hCG beta-C3d3 (C1-3 groups), or pCMV4-hCG beta-C3d3 (D1-3 groups), at dosage of 5 pmol, 10 pmol, and 20 pmol, respectively. Three weeks after the second vaccination the animals were killed, specimens of their peripheral blood were extracted to determine the anti-hCG beta antibody titer by indirect ELISA. Their spleen cells were harvested and stimulated in vitro by hCG antigen for 24 hours. The Th1/Th2 cytokines in the culture supernatant were determined by ELISA., Results: At the dosage of 20 pmol, C3d molecular adjuvant significantly enhanced the anti-hCG beta antibody titer. The utmost anti-hCG beta antibody titer of C3 group was 1:450, 9 times higher than that of B3 group, and the utmost anti-hCG beta antibody titer of D3 group was 1:12 150, 243 times higher than that of B3 group. Stimulated in vitro by 5,000 IU hCG beta antigen, the splenic cells of the C3 and D3 immunization group produced significantly lower IL-2, INF-gamma and TNF-alpha than those of the B3 immunization group (P < 0.01 or P < 0.05). The IL-4 level of the C3 group was higher than that of the B3 group while the IL-10 level of the D3 group was significantly higher than that of the B3 group (P < 0.01)., Conclusions: The C3d molecular adjuvant increases significantly the hCG beta immunogenicity of hCG beta DNA vaccination; meanwhile decreases the secretion of Th1 cytokines (IL-2, INF-gamma, and TNF-alpha), and increases the expression of Th2 cytokines (IL-4 and IL-10) in response to hCG antigen. So C3d changes the anti-hCG immune response from Th1 type to Th2 type.

Epstein-Barr virus, the causative agent of mononucleosis and several human cancers, infects cells via complement receptor type 2 (CR2). Expression of this receptor is restricted to B lymphocytes, some epithelial cells and immature thymocytes; expression of CR2-like proteins has been also found on T cells. In the present report, we identified the presence, on the membrane of Li7A cells, of a novel EBV receptor distinct from CR2 capable of triggering fusion with EBV virions with more rapid kinetics than that found with lymphoblastoid cells (Raji).

We demonstrate herein that p16, a 16 amino acid synthetic peptide derived from human C3d, which carried LYNVEA sequence of C3d reacting with CR2 and C3d present in trypsin-cleaved C3, triggered "in vitro" and "in vivo" phosphorylations and "in vitro" proliferation of human B lymphocytes, depending on the stage of cell differentiation. Indeed, p16 and C3dT induced "in vivo" tyrosine phosphorylation of pp105 and "in vitro" proliferation only of CR2-positive and not of CR2-negative cell lines. In addition, p16 and C3dT also induced "in vivo" tyrosine phosphorylation of pp100 and "in vitro" proliferation of only small dense resting B lymphocytes and not other B lymphocyte subpopulations nor T lymphocytes. These data suggest that induction of pp100 and pp105 phosphorylation by p16 and C3dT could represent an early event associated with expression of CR2 in the regulation of human B lymphocyte proliferation.

We present herein the first evidence that human C3 and, with a higher efficiency, trypsin-cleaved C3 enhanced in vitro phosphorylation of a cellular component, characterized by an apparent molecular weight of 105 kDa, pp105, present in the human B lymphoma cells, Raji. This regulatory activity was associated with C3d fragment generated in trypsin-cleaved C3. A 16 amino-acid peptide, carrying the LYNVEA sequence of C3d reacting with the C3d receptor (CR2), was synthetized. P16 enhanced, in a dose-dependent curve between 0.3 to 10 microM, in vitro phosphorylation of pp105, as well as C3d fragments present in trypsin-cleaved C3. A fibrinogen-related synthetic peptide of 15 amino acids, used as control, had no effect on pp105 phosphorylation. P16 and trypsin-cleaved C3 regulate pp105 phosphorylation through identical pathways. Thus, p16 represents the 16 amino-acid sequence of C3 which regulated in vitro phosphorylation of pp105.