SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Human and rat alveolar macrophages produce haemolytic C2 during in vitro culture. We conclude that C2 synthetic ability is maintained during in vivo maturation of human monocytes to macrophages and that production of complement components by mature tissue macrophages may be important for optimal generation of inflammatory responses.
The deficiency of second component of complement (C2d) is the most common hereditary complement deficiency. Patients with C2 deficiency are frequently associated with an auto-immune disease process, in particular, systemic lupus erythematosus (LE)-like syndrome and/or vasculitic syndrome or bacterial infections. C2d has been associated with the LE subset of subacute cutaneous LE (SCLE), the presence of anti-Ro (SSA) antibodies, and the human leukocyte antigen (HLA) types A10, B18, DR2. We describe the clinical, serologic and immunogenetic data in a patient with manifestations of Sjögren's syndrome who developed urticarial vasculitis and photosensitive annular SCLE which were effectively treated with oral dapsone. Our case illustrates the dynamic nature of LE.
C4 allotyping 13 homozygous C2-deficient individuals demonstrated 23 of 25 haplotypes to be of the relatively rare type C4A4 B2. This is of the same magnitude as the association of C2Q0 with HLA-DW2/DR2.
Genetic polymorphisms of the serum complement components (C2, C4, C6, and C7) and HLA-antigens were studied in Japanese patients with psoriasis vulgaris. Among these complement components, positive associations with C4A4 and C4B2 were obtained. In addition to the previously reported haplotypes HLA-Cw6-B13 and Cw6-Bw57-DR7, the extended haplotype HLA-Cw11-Bw46-C4A4. 4B2-BFS-C2C-DRw8 may be a high risk haplotype in Japanese patients with psoriasis vulgaris.
Legionella pneumophila has previously been shown to require serum factors for efficient uptake by phagocytic cells. In this investigation, the roles of specific antibody and complement in phagocytosis of L. pneumophila by human polymorphonuclear leucocytes (PMN) and tissue macrophages were determined. Opsonization was assessed by quantitating the uptake of [3H]-labelled Legionellae. Compared to other Gram-negative and to Gram-positive bacterial species, L. pneumophila was highly resistant to the opsonic activity of normal pooled human serum (PHS). Of 12 donor sera tested, only four promoted significant L. pneumophila uptake when used at full strength. Experiments with immune antibody, and with human sera deficient in immunoglobulins, or the complement components C2, C3, or C5, revealed that L. pneumophila opsonization was dependent on antibody-mediated activation of the classical complement pathway; activation of the alternative pathway could not be detected. At high concentrations, immune antibody alone could adequately opsonize L. pneumophila. Human alveolar and peritoneal macrophages required very similar amounts and types of opsonins for L. pneumophila phagocytosis as did human PMN. Heating L. pneumophila to temperatures greater than or equal to 80 degrees abolished its resistance to opsonization by diluted PHS; however, activation of complement via the alternative pathway or via other antibody-independent routes remained undetectable. These studies show that, in addition to immune antibody, the classical pathway of complement plays an important role in the opsonization of L. pneumophila. The limited ability of these bacteria to interact with human complement provides a likely explanation for their resistance to opsonization and may be partly based on heat-sensitive structures on the surface of L. pneumophila.
Explore the source record for details and available documents.
We have measured the changes in C2 production and in cyclic nucleotide levels in mononuclear leucocytes cultured in the presence of agents which change intracellular cAMP. Adenylcyclase activators, cholera toxin and phosphodiesterase inhibitors increased cAMP levels and reduced C2 production. Imidazole, hydrocortisone and prostaglandin synthetase inhibitors reduced cAMP and increased C2 synthesis. The level of cAMP after 2 hr incubation showed an inverse correlation with C2 levels in the culture supernatants. When histamine, which increases cAMP and reduces C2 production, and imidazole, which reduces cAMP and increases C2 synthesis, were added together, levels of cAMP and C2 did not differ significantly from those found in control cultures. On the basis of these observations we have concluded that changes in monocyte cAMP alter the production of C2.
Explore the source record for details and available documents.
Mannan-binding lectin (MBL)-associated serine proteases-1 and 2 (MASP-1 and MASP-2) are homologous modular proteases that each interact with MBL, an oligomeric serum lectin involved in innate immunity. To precisely determine their substrate specificity, human MASP-1 and MASP-2, and fragments from their catalytic regions were expressed using a baculovirus/insect cells system. Recombinant MASP-2 displayed a rather wide, C1s-like esterolytic activity, and specifically cleaved complement proteins C2 and C4, with relative efficiencies 3- and 23-fold higher, respectively, than human C1s. MASP-2 also showed very weak C3 cleaving activity. Recombinant MASP-1 had a lower and more restricted esterolytic activity. It showed marginal activity toward C2 and C3, and no activity on C4. The enzymic activity of both MASP-1 and MASP-2 was specifically titrated by C1 inhibitor, and abolished at a 1:1 C1 inhibitor:protease ratio. Taken together with previous findings, these and other data strongly support the hypothesis that MASP-2 is the protease that, in association with MBL, triggers complement activation via the MBL pathway, through combined self-activation and proteolytic properties devoted to C1r and C1s in the C1 complex. In view of the very low activity of MASP-1 on C3 and C2, our data raise questions about the implication of this protease in complement activation.
A case of systemic lupus erythematosus associated with an homozygous deficiency in the second fraction of complement is reported and compared to previous reports of the literature. The high incidence of infections in these patients is outlined. The defective gene in this family was associated with the HLA A10B18 haplotype and the propositus was homozygous at the HLA-D locus. Familial study allowed the detection of 3 heterozygous individuals two of them being symptomatic (vascular purpura, high incidence of bacterial infections).
Adenosine inhibits C2 production by human monocytes. The use of synthetic analogues of adenosine suggested that the action was mediated by receptors of A2 type. EHNA which inhibits the enzyme adenosine deaminase and increases the concentration of intracellular adenosine also reduces C2 production. It is therefore possible that endogenous adenosine regulates C2 synthesis.
Explore the source record for details and available documents.
The gene coding for properdin factor Bf is located in the human major histocompatibility complex and is closely linked to the genes coding for the complement components C2 and C4. Recently, by Southern blotting techniques, a restriction fragment length polymorphism was identified using the endonuclease Taq I, which subdivides haplotypes carrying the F allele of factor Bf. The F allotype has also been subdivided at the protein level by isoelectric focusing into two subtypes Fa and Fb. We have investigated the DNA of 41 healthy unrelated individuals with known BfF subtypes using the 2.3 kb factor Bf cDNA probe to determine if there is any correlation between the Taq I polymorphism and F subtype. We have found that in 23 individuals who carried the Fb subtype a 6.6 kb Taq I fragment was present. The remaining 18 individuals carried the Fa subtype and showed only the 4.5 kb Taq I fragment on Southern blotting (P = 10(-12). This striking correlation (r = 1) between the Fb protein and DNA polymorphism is surprising especially as the 4.5 kb and 6.6 kb Taq I fragments overlap the Bf and C2 genes and the polymorphic Taq I site is located within the C2 gene.
A human hepatoma cell line, associated with thorotrast exposure, from an hepatitis B marker-negative patient was established as a permanent cell line (Mz-Hep-1) in tissue culture. Histology of the primary tumor, as well as phase contrast, transmission and scanning electron microscopy of the cultured cells showed typical characteristics of liver cells. Mz-Hep-1 cells secreted complement components (C2, C3, C4), carcinoembryonic antigen, lactate dehydrogenase, chymotrypsin, haptoglobin and retinol-binding protein and expressed HLA-, transferrin-, blood group B-related determinants and complement component C5 and carcinoembryonic antigen on their cell surface. Mz-Hep-1 cells represent the first human hepatoma cell line, which is strongly associated with a carcinogen.
Explore the source record for details and available documents.
C2 synthesis by human peripheral blood monocytes cultured in the presence of human alpha-interferon (IFN-alpha) was studied. IFN-alpha was added in different amounts (1-1000 IU/ml) to the cultures on day 3 and was removed on day 7. As control, mock interferon (m-IFN) was also tested. C2 content of the culture supernatants was measured by immunohaemolytic method. IFN-alpha was found to enhance C2 synthesis in a dose-dependent way. The enhancing effect could be observed even after the removal of IFN-alpha. C2 production by the cultured monocytes was increased by m-IFN as well; the extent of enhancement however, was found to be significantly lower than that induced by the corresponding amount of IFN-alpha. In contrast to the enhancing effect on C2 production, IFN-alpha did not influence total protein synthesis in the cultures, suggesting a selective stimulatory action on the C2 gene.
The expression of complement receptors by human follicular dendritic cells (FDC) was investigated by immunohistochemical techniques by using polyclonal and monoclonal antibodies to antigenic determinants of CR1, CR2, and CR3. Upon optical immunohistochemical examination of frozen sections from human reactive lymph nodes and tonsils by a three-step immunoperoxidase technique, a strong staining of cell bodies and cytoplasmic extensions of FDC was observed in germinal centers with anti-CR1 and anti-CR2 antibodies. Staining for these antigens was also found on cytoplasmic extensions of FDC in the mantle zone and on the plasma membrane of B cells in the entire follicles. Staining of FDC with anti-CR2 antibody was more intense than that of B lymphocytes. Monoclonal antibodies directed against epitopes of the alpha-chain of CR3 weakly stained FDC in follicles in a similar pattern to that which was observed on adjacent sections with mouse monoclonal antibody KIM4 that only recognizes FDC in human lymph nodes. Immunoelectron-microscopy was performed on frozen sections of a lymph node involved with a centroblastic centrocytic B malignant lymphoma and a reactive tonsil with the use of rabbit F(ab')2 anti-CR1 antibodies and mouse monoclonal anti-CR2 antibody. All the plasma membrane of the cell body and cytoplasmic extensions of FDC in germinal centers and in the mantle zones homogeneously stained for CR1 and CR2 antigens. Fibroblastic reticulum cells were negative. The plasma membrane of tumoral B lymphocytes strongly stained with anti-CR1 and weakly stained with anti-CR2 antibodies. The presence of CR1, CR2, and CR3 on FDC is a unique surface characteristic of these cells that should optimally allow the cells to bind antigen/antibody complexes bearing any type of C3 fragment.
Explore the source record for details and available documents.