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At least 55 records · Page 3Linked to original sources
PubMed1976

Thermal fragmentation of Escherichia coli beta-galactosidase. Isolation and characterization of an alpha-complementing and two non-complementing polypeptide fractions.

Carboxymethylated Escherichia coli beta-galactosidase EC 3.2.1.23 could be broken to polypeptides of fairly uniform size (average molecular weight about 22,000 daltons) by heating for less than or equal to 8 h at 100 degrees C and pH 7.5 IN 8 M-urea. Using phosphocellulose chromatography in NaCl-urea gradients, the resulting polypeptide mixture could be resolved in three fractions essentially homogeneous by disc gel electrophoresis in urea at several pH values, and by isoelectric focusing. One of these fractions was active as alpha-donor in in vitro complementation of beta-galactosidase activity with Escherichia coli mutant M15; this activity was largely retained after CNBr cleavage. All three fractions carried arginine as carboxyl-terminal amino acid. No significant amount of any specific amino could be detected in NH2-terminal position.

Amino Acids↗
PubMed1976

Mechanism of injury of virus-infected cells by antiviral antibody and complement: participation of IgG, F(ab')2, and the alternative complement pathway.

Antibody-mediated C-dependent lysis of cell lines infected with herpes simplex type 1 virus, influenza A degrees virus, measles virus, and mumps virus occurred by the alternative C pathway with the participation of IgG antibodies. Lysis occurred only with immune human sera, Mg++ EGTA immune sera, and immune sera depleted of C4 or treated with Fab anti-C4. Lysis did not occur with nonimmune sera, Mg++ EDTA immune sera, and immune sera heated 50 degrees C for 25 min, depleted of factor B or treated with Fab antifactor B. Lysis was restored to heated and factor B immunodepleted immune sera by addition of factor B, but not by addition of an excess of C2. Further studies showed that lysis of HeLa cells infected with measles virus was induced by both immune IgG and F(ab')2 but not Fab' in the presence of a nonantibody-containing human C source. Lysis of measles virus-infected cells was also indpendent of movement of viral antigens on the surface of the infected cells, as inhibition of viral antigen capping by cytochalasin B or sodium azide was not associated with abrogation of immune lysis.

Antibodies, Viral↗
PubMed1975

Interactions of the third component of complement (C3) with cross-linked dextran. III. Isolation and characterization of interacting components after enzymatic digestion of complement coated cross-linked dextran.

In previous investigations we could show that incubation of cross-linked dextran (Sephadex) with normal human and normal guinea pig serum results in the binding of C3 to Sephadex. This binding was found to be due to activation of C3 via an alternate pathway. In this paper data are presented which show that components bound to Sephadex can be recovered after enzymatic digestion of serum-reacted Sephadex beads. The digests were characterized with immuno-electrophoresis and double immunodiffusion techniques. It could be shown that the main component present in the digest was converted C3. Apart from C3 under our test conditions only minute amounts of C3A but no other serum proteins were detectable. The observation that almost exclusively C3 is bound to Sephadex is further supported by the finding that immunization of rabbits with serum-reacted Sephadex beads results in the exclusive formation of anti C3 antibodies. Implications from these findings and possible applications are discussed.

Antibody Formation↗
PubMed1978

Leukocyte complement: assembly of the membrane attack complex of complement by human peripheral blood leukocytes in the presence and absence of serum.

The specific neoantigenic determinants (neoAg) that are indicative of the assembled C5b-9 C complex are generated on the surface of peripheral blood leukocytes (PBL) during collection and processing of blood. Formation of neoAg on PBL could be prevented by collecting blood directly into 20 mM EDTA and, could be induced in vitro by adding autologous serum to isolated PBL that lacked neoAg. When neoAg was induced by the addition of serum containing 125I-labeled C8, the C8 was incorporated into a 23S complex which could be eluted from PBL. A mechanism for neoAg formation on PBL independent of exogenous serum factors was detected when PBL were placed into culture in serum-free medium. Results with metabolic inhibitors and 14C-leucine suggest that PBL can synthesize C5 and assemble the C5b-9 complex. The possible relevance of these findings to the understanding of mechanisms of cell-mediated cytotoxicity is discussed.

Antigens↗
PubMedDate not supplied

The complement system in host defense and inflammation.

In this discussion I have reviewed the major role of complement in host defense and inflammation. In addition, I have discussed dificiency states. Although these are rare, their clinical signs and symptoms can be predicted, at least in part, on the basis of our current understanding of the biological activities of complement and the various pathways of complement activation. This is not to say that complement plays no role in a wide variety of other illnesses. However, when complement plays a role in an illness, often this is not because it is functioning in an aberrant fashion. The usual situation is that complement is being activated and is serving its normal function in causing inflammation and damage to tissues under abnormal circumstances. Thus, for example, circulating antigen complexes may be deposited in the kidney, activate complement, and mediate tissue inflammation. In this case, complement is functioning normally but is being activated under abnormal circumstances. The same type of analysis can be made for many diseases of many different organ systems. At present, we have no drugs that are effective in humans in controlling the activation of complement and complement-mediated inflammation. We have not yet even established whether local variations in the activity of complement may affect the course of a clinical infection, but there is certainly strongly suggestive evidence to support this idea. It should be clear that under certain circumstances complement may well be a major factor in controlling the course of an infection. The near future should bring a vast expansion in our understanding of how complement contributes to specific clinical illnesses and to the defense of the host against specific microorganisms.

Angioedema↗
PubMed2026

Complement expression profiles in human glomerular mesangial cells, endothelial cells, podocytes and proximal tubular epithelial cells.

BACKGROUND: Local expression of complement components in the kidney has been reported sporadically in both diseased and normal kidneys. This study aimed to comprehensively characterize the expression of complement components in human glomerular mesangial cells (GMCs), glomerular endothelial cells (GECs), podocytes, and proximal tubular epithelial cells (PTECs) in non-diseased renal tissue. METHODS: Complement expression in cultured human renal intrinsic cells was initially evaluated using reverse transcription polymerase chain reaction and immunofluorescence staining. These findings were further examined using publicly available single-cell RNA-sequencing datasets and 10×Genomics single-cell RNA sequencing of non-diseased human kidney tissue. The analyses focused on complement components involved in the initiation of the classical, lectin, and alternative pathways, as well as components shared among these activation pathways, terminal pathway components, complement regulators, and complement receptors. RESULTS: Complement components unique to the initial phase for classical pathway (C1S, C1R, C2, C4), lectin pathway (MBL2, FCN1, MASP1), alternative pathway (CFB, CFD), and the C3 component shared by the three activation pathways were detected in these cells. The components shared by the terminal pathways including C5, C6, C7, C8 and C9 exhibited lower expression, while complement regulators (CFH, CFI, CD55/DAF, CD46/MCP, CD59, C4BPB, PROS1/Protein S) or receptors (CD93/C1QR1, CR1), particularly membrane-bound proteins, such as DAF, MCP and CD59, which inhibit complement activation and the formation of the membrane attack complex, showed relatively high expression. CONCLUSION: These results showed that all four types of intrinsic renal cells expressed multiple complement components associated with the classical, lectin, and alternative pathways. In non-diseased kidney tissue, complement regulatory molecules involved in the control of complement activation showed relatively higher expression, whereas components of the terminal complement pathway were expressed at relatively lower levels, suggesting that renal intrinsic cells maintain a locally poised but tightly regulated complement system.

Humans↗
PubMed2026

The complement system in inflammatory bowel disease: from early observations to emerging frontiers.

PURPOSE OF REVIEW: The complement system is one of the most evolutionarily conserved arms of innate immunity and has re-emerged as an important regulator of intestinal inflammation in inflammatory bowel disease (IBD). Early observations from the mid-1970 s such as complement deposition in diseased bowel tissue and elevated serum complement levels in patients with ulcerative colitis and Crohn's disease have evolved into a nuanced understanding of how individual complement components can exert both protective and pathogenic effects in IBD. This review highlights recent advances in complement biology and examines how complement shapes intestinal immune responses, particularly in the setting of ongoing inflammation. RECENT FINDINGS: The complement system consists of more than 60 proteins that act as rapid first responders to infection. Although traditionally considered primarily liver-derived circulating effectors, recent work has demonstrated local synthesis and activation of key complement components at mucosal sites, including the colon. In parallel, genome-wide association studies have identified variants in complement genes associated with severe IBD complications. Collectively, these findings reveal a dichotomous role for complement in IBD, whereby excessive activation promotes inflammation, while impaired function compromises host defense and worsens disease outcomes. SUMMARY: Complement-targeted therapies have been effective in other diseases but have not yet translated to IBD. A deeper understanding of context-dependent protective versus pathogenic complement functions will be essential for developing future therapeutic strategies.

Humans↗