| C-reactive protein (CRP) is an acute phase protein that binds to human and murine Fcgamma receptors FcgammaRI and FcgammaRII) on immune cells and activates the classical complement pathway. CRP also binds to phosphocholine (PC) determinants on the C-polysaccharide of S. pneumoniae and to FcgammaR on bone marrow derived DC. It is well documented that CRP protects mice from lethal systemic S. pneumoniae infection and more recently CRP in respiratory secretions has been found to have complement-dependent microbicidal activity.; The experimental vaccine paradigm presented in this dissertation employs DC loaded ex vivo with CRP-opsonized R36a to induce an elevated antibody response to PspA. We proposed that because of the potent adjuvant properties of DC and the protective effects of CRP, using CRP-opsonized S. pneumoniae to pulse DC ex vivo would be an effective antigen delivery system to present antigen to T cells and increase antibody responses to bacterial antigens including PC and PspA.; The purposes of this study were first, to determine if CRP affected the phagocytosis and subsequent presentation of R36a by murine bone marrow derived DC, second to determine if CRP affected the antibody response to both protein (PspA) and polysaccharide (PC) and third to test the protective capacity of the induced antibody response against a virulent challenge. Furthermore, because CRP binds to FcgammaRI on DC and other immune cells, mice lacking functional FcgammaRI due to a deficiency of the FcR gamma-chain, were also evaluated for any effects attributed to CRP.; To evaluate the effect of CRP on phagocytosis, wild type DC and FcR gamma-chain deficient DC were pulsed with either unopsonized R36a or CRP-opsonized R36a in the presence and absence of cytokines for various time periods. Results indicate that CRP significantly increased the uptake of R36a by C57BL/6 DC, while only slightly increasing the uptake of R36a by FcRgamma-chain deficient cells. The increased uptake was directly attributed to the ability of CRP to act as an opsonin and not due to agglutination. The ability of CRP to increase phagocytosis was found to be gamma-chain dependent. (Abstract shortened by UMI.)... |
