Biomedical subjects

V M Avery

Publications and source records attributed to V M Avery.

6 recordsLinked to original sources

PubMed1993

Characterization of factor H binding to human polymorphonuclear leukocytes.

Previous studies indicate that factor H (fH) binds to a number of cell types and may have functions other than C regulation. We have examined for fH binding to PMN using flow cytometry and radiolabeled binding assays. Binding of fH was demonstrated to be specific and saturable with approximately 6 x 10(4) binding sites/polymorphonuclear leukocytes (PMN) and a Ka value of 3.3 x 10(8) L/M. Binding of fH to PMN was ionic strength dependent, required divalent cations, and was enhanced by PMN stimulation with FMLP and calcium ionophore, A23187. The 38-kDa N-terminal tryptic fragment of fH bound to PMN and blocking experiments with mAb suggested a receptor binding site was located within the fifth SCR of fH. fH binding was not due to associations with surface-bound C3 or to CR3. Binding of fH to U937 and Raji cells, but not to T cells was also demonstrated. These studies provide presumptive evidence for a fHR on PMN. Binding of fH by fHR could enhance recognition of opsonized targets, trigger secondary intracellular events or contribute to intrinsic protection of cells against C.

Amino Acid Sequence↗

PubMed1993

Detection of mosaic protein mRNA in human astrocytes.

Mosaic proteins consist of a group of proteins that may be comprised of one or more types of a variety of different structural modules and have a diverse range of functions. We have examined primary human astrocyte cultures for the presence of three mosaic proteins, B2I and the complement proteins factor H and properdin. Using the polymerase chain reaction and an enhanced chemiluminescence detection technique, we were able to show that mRNA transcripts for each of these proteins are expressed in human astrocytes.

Astrocytes↗

PubMed1992

Detection of complement protein mRNA in human astrocytes by the polymerase chain reaction.

Primer sets specific for complement proteins, C3, factor B and factor I, were designed and used to amplify cDNA from cultured human astrocyte mRNA by the polymerase chain reaction. Appropriately sized PCR products of 506 bp, 885 bp and 146 bp, respectively, were generated and specificity was confirmed with Southern blotting using an enhanced chemiluminescence detection system. The sensitivity of detection was high, with amplified product from cDNA of approximately 6250 cells readily visualized. C3 and factor B have previously been reported to be produced by murine astrocytes; however, this is the first report indicating synthesis of C3, factor B and factor I by human astrocytes. These results indicate that PCR is a simple and sensitive technique to detect mRNA transcripts for proteins of the alternative pathway of complement in human astrocytes.

Astrocytes↗

PubMed1991

Antibacterial properties of breast milk: requirements for surface phagocytosis and chemiluminescence.

The opsonic components of breast milk responsible for phagocytosis of surface-adherent Staphylococcus aureus by human polymorphonuclear leukocytes were investigated. There was significantly greater phagocytosis of bacteria pre-opsonized with 100% breast milk than of unopsonized bacteria (p less than 0.001). Heat inactivation of breast milk had no effect on surface phagocytosis, indicating that phagocytosis is independent of complement. The predominant immunoglobulin in breast milk, secretory immunoglobulin A (IgA), did not promote phagocytosis. In contrast, IgG, which is present in very low amounts in breast milk (0.05 mg/ml), was as opsonic as 100% breast milk, suggesting that this is the major opsonin. An oxidative burst as measured by chemiluminescence was observed during phagocytosis of bacteria pre-opsonized with 100% breast milk. Heat inactivation of breast milk reduced the chemiluminescence response to the level of control. Neither secretory IgA nor IgG stimulated a polymorphonuclear leukocyte chemiluminescence response to surface-adherent bacteria. These experiments indicate that IgG is the principal component of breast milk responsible for surface phagocytosis but that complement is required for the generation of chemiluminescence and thus may be essential for intracellular killing of bacteria. Secretory IgA, despite its abundance in breast milk, has no effect on surface phagocytosis or neutrophil chemiluminescence.

Humans↗

PubMed1990

Surface phagocytosis and host defence in the peritoneal cavity during continuous ambulatory peritoneal dialysis.

Since patients on continuous ambulatory peritoneal dialysis are at high risk for peritonitis, the opsonins in peritoneal dialysis effluent responsible for phagocytosis and a neutrophil chemiluminescence response to surface-adherent Staphylococcus epidermidis were examined. In surface phagocytosis assays uninfected dialysate was as opsonic as 1% serum. The opsonic activity was heat stable and equal to that of purified IgG at the same concentration (0.1 mg/ml). In contrast, optimal chemiluminescence to surface-adherent Staphylococcus epidermidis was dependent on complement. C3 deposition on Staphylococcus epidermidis opsonized in dialysate was quantitated by an enzyme immunoassay (EIA) and represented 13% of control C3 deposited with opsonization in 10% serum. Unused dialysate was found to be inhibitory to neutrophil phagocytosis and complement deposition. A combination of the low pH and high dextrose concentration of dialysate was responsible, but restoration of the pH to 7.4 largely restored both indices. During peritonitis there was a parallel increase in IgG levels and C3 deposition (r = 0.8), and surface phagocytosis was also enhanced. On further analysis, subjects with a single episode of peritonitis had a significantly more opsonic peritoneal effluent than those who had two infections during the study. This latter group had a poor IgG response to infection. This study demonstrates the relative deficiencies of host defence in the peritoneal cavity and indicates that measures to improve opsonin delivery and reduce the inhibitory effects of dialysate would be beneficial.

Aged↗

PubMed1989

Surface phagocytosis of Staphylococcus epidermidis and Escherichia coli by human neutrophils: serum requirements for opsonization and chemiluminescence.

We examined the serum requirements for surface phagocytosis of Staphylococcus epidermidis and Escherichia coli and for the subsequent chemiluminescent response of human neutrophils. Substantial surface phagocytosis of S. epidermidis occurred in the absence of opsonins, although the presence of 10% pooled or heat-inactivated serum significantly increased phagocytosis. There was no significant difference between these opsonins, indicating that surface phagocytosis of S. epidermidis did not require complement. Unopsonized E. coli were not as readily phagocytized as S. epidermidis (33% versus 57%). In contrast to S. epidermidis optimal phagocytosis of E. coli required complement as 10% heat inactivated donor serum (HHS) was significantly less effective as an opsonin than 10% pooled healthy donor serum (PHS). The time kinetics for phagocytosis of each organism were similar, with most of the phagocytosis occurring in the first 10 min. The chemiluminescent response of neutrophils produced discrepant results. Maximal chemiluminescence was observed when neutrophils were stimulated with bacteria opsonized in PHS. The response to HHS-opsonized bacteria was less, and chemiluminescence to unopsonized bacteria was only marginally higher than the control, even though there was relatively good phagocytosis. These results define the opsonic requirements for surface phagocytosis of S. epidermidis and E. coli and indicate that although complement may not be required for phagocytosis, it is necessary for generation of a maximal oxidative burst, and thus may be essential for efficient intracellular killing.

Blood Bactericidal Activity↗