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Biomedical subjects

A Orren

Publications and source records attributed to A Orren.

At least 37 records · Page 2Linked to original sources
PubMed1994

C6 haplotypes: associations of a Dde I site polymorphism to complement deficiency genes and the Msp I restriction fragment length polymorphism (RFLP)

Complement C6 has a common charge polymorphism designated A and B with gene frequencies of 0.65 and 0.35. The probable molecular basis for this is a Glu (C6A) for Ala (C6B) substitution at amino acid position 98, and is detected by digestion with the restriction enzyme Dde I of a polymerase chain reaction (PCR)-amplified fragment of genomic DNA. C6A was found to be Dde I-positive and C6B corresponds to Dde I-negative. We have applied our Dde I A/B polymorphism genotyping method to the investigation of C6-deficient individuals with complete (C6Q0) and sub-total deficiency (C6SD) protein phenotypes, including members of four families. We have also investigated the RFLP detected by digestion of genomic DNA with the enzyme Msp I, which is due to a polymorphic site located in the 5' section of the gene, the variable sequence of which has yet to be determined. Sixteen out of seventeen unrelated C6Q0 subjects were found to be genotypically Dde I B/Msp I-negative; the remaining subject was heterozygous at both the loci under investigation. The C6SD phenotype was found to be associated with the Dde I A/Msp I-positive genotype in two families with combined C6/C7 subtotal deficiency and two with C6SD. It can be concluded that the two forms of C6 deficiency, C6Q0 and C6SD, arose independently on two different C6 allelic backgrounds. These associations have allowed the genotyping of the rare families that contain both types of deficiency. We have also defined a number of normal C6 Dde I/Msp I haplotypes in Caucasians and Cape Coloured populations.

Adult↗
PubMed1994

A novel human complement component C7 phenotype detected in South Africa and proposed designation of the allele as C7*10.

A novel allotype of the seventh component of human complement was detected by isoelectric focusing. The band pattern showed a complete band-interval shift towards the cathode compared with the C7 1 allotype and it is proposed that the designation is C7 10. The allele C7*10 segregated in two South African Cape Coloured families and had a gene frequency of 0.006. It was also found to segregate together with a C6*rare allele.

Alleles↗
PubMed1994

Characterization of strains of Neisseria meningitidis recovered from complement-sufficient and complement-deficient patients in the Western Cape Province, South Africa.

Complement deficiency has been associated with increased susceptibility to meningococcal disease. In order to determine whether special meningococcal strains caused disease in complement-deficient (CD) patients, 17 Neisseria meningitidis strains recovered from patients in the Western Cape Province, South Africa, known to be CD were compared with 124 routine isolates obtained from patients living in the same area. Serogrouping of the strains from the CD subjects revealed that the common serogroups, particularly serogroup B, predominated. However, the prevalence of rare serogroups among isolates from CD subjects was significantly higher than that found among isolates from the control group. Sero- and subtyping of the class 1 and class 2 or 3 outer membrane proteins showed no significant difference between isolates from CD subjects and the routine clinical isolates. Multilocus enzyme electrophoresis of the 141 isolates revealed six clusters of electrophoretic types (ETs) and two unrelated ETs. The same degree of genetic diversity existed in ETs of isolates from CD subjects and the control group. However, the ET-5 complex, which is known to be associated with epidemic disease, was found in 22 (18%) of the routine clinical isolates but in none of the isolates from the CD subjects. This difference was marginally significant. What was highly significant was the finding that 8 of the 17 isolates from CD subjects were in one ET cluster, cluster F, which comprised a total of 20 isolates. Thus, our results show a difference in the clonal compositions of the strains that infect CD subjects in comparison with the clonal compositions of those that cause clinical infections in the population at large.

Adolescent↗
PubMed1994

Paradoxical reconstitution of complement activity following plasma transfusion of an individual with deficiency of the seventh component of complement.

A subject deficient in the seventh component of complement (C7) was plasmapheresed with 660 ml C7-sufficient plasma. The expected reconstitution of C7 activity, followed by exponential decay, was not observed. During day 1, serum haemolytic C7 and total haemolytic complement were undetectable and C7 levels were very low by C7 ELISA. However, low levels of circulating fluid phase terminal complement complex (TCC) were detected. On day 2 about microgram C7/ml serum was detected and this rose to 6 micrograms/ml by day 17. Functional complement activity was also present. At day 28 the serum C7 and total haemolytic complement had dropped to pretransfusion levels. A low level of C5b6 was present in pretransfusion serum and this increased markedly immediately following transfusion when the patient's serum also acquired C7 consuming activity. Throughout the study low levels of anti-C7 antibodies were present but there was no evidence that antibody was directly responsible for the C7 consumption. Nevertheless antibody-antigen interactions could have generated circulating C5b6. C5b6 has been shown previously to have the capacity to inhibit C7 activity in vitro. Investigations of the C7 circulating on days 2-17 demonstrated normal molecular weight, functionally active C7. The donor sera and the recirculating C7 allotyped C7-1 by isoelectric focusing; however, the recirculating C7 showed additional weak bands with C7 functional activity, suggesting a possible genetic or acquired abnormality. Although the disappearance of C7 immediately post-transfusion may be explained by the presence of C5b6, there is no satisfactory explanation for the rising C7 levels on days 2-17 and we cannot exclude temporary C7 secretion by the patient.

Adult↗
PubMed1993

Association of a 12.5-kilobase allele of the MspI restriction fragment length polymorphism of the C6 gene in patients with total deficiency of the sixth component of complement.

The distribution of MspI restriction fragment length polymorphism (RFLP) alleles was investigated using the C6-PVX probe of the sixth component of complement (C6) and DNA from lymphocytes of 11 patients with homozygous C6 deficiency (C6Q0), 18 of their family members, 3 patients with subtotal C6 deficiency (C6SD) and 28 normal C6-sufficient controls. A biallelic polymorphism of 12.5- and 8.2-kb RFLP alleles was observed, and co-dominant inheritance of the two alleles was demonstrated in family studies. All 11 C6Q0 patients were homozygous for the 12.5-kb allele; this includes 8 unrelated propositi. The gene frequencies for both the 12.5- and 8.2-kb alleles in control subjects were 0.5, and the association of C6*Q0 with the 12.5-kb allele was found to be highly significant (p = 0.0001). Family studies in a C6Q0 family demonstrated that the MspI polymorphism may be used to trace C6*Q0 heterozygous carriers. Studies in families with C6SD, when considered with the results of C6 and C7 allotyping, showed definite co-segregation of C6*SD with the MspI 8.2-kb allele in one family and very probable co-segregation in another. All 11 South African C6Q0 subjects were homozygous for the C6Q0/MspI 12.5-kb/C7 M haplotype. Our data describe new associations of C6 deficiency genes which may assist in the future identification of the molecular defects.

Alleles↗
PubMed1992

Meningococcal septicaemia in a C6-deficient patient and effects of plasma transfusion on lipopolysaccharide release.

Patients whose blood is deficient in the terminal component of complement have an increased susceptibility to meningococcal infection. However, mortality from meningococcal infection is lower in these patients than in immunocompetent subjects. We studied a C6-deficient patient with meningococcal sepsis who received fresh frozen plasma (FFP). The patient's initial plasma endotoxin, C6, and terminal-complement-complex concentrations were low, but rose sharply after treatment with FFP. Samples of the patient's serum taken shortly after admission did not cause endotoxin release from Escherichia coli J5 in vitro, but endotoxin-releasing activity was restored in serum samples taken after infusion of FFP. It is possible that C6-deficient patients have reduced mortality from meningococcal infection because their serum cannot cause acute release of endotoxin from the invading organism and extensive tissue damage is thus avoided.

Adult↗
PubMed1992

C7 M/N protein polymorphism typing applied to inherited deficiencies of human complement proteins C6 and C7.

C7 M/N typing, the determination of the complement component C7 M/N phenotypes, was successfully used in family studies to trace haplotypes bearing C7 deficiency genes. Furthermore, it was shown to be preferable to C7 allotyping based on isoelectric focusing (IEF) since it distinguishes two common alleles (C7*M and C7*N), whereas one common C7 IEF allele (C7*1) predominates in most populations. It is also the more sensitive method, as it enabled detection of very low amounts of abnormal C7 molecules in the third generation of a combined subtotal C6/C7-deficient subject and thus confirmed that this partial deficiency gene is not silent in heterozygotes. In this respect C7 M/N typing is even more informative than DNA restriction fragment length polymorphism typing which will assess the presence but not necessarily the functional status of a gene. C6 and C7 genes are tightly linked and therefore C7 M/N typing was also applied to tracing C6 deficiency genes in families. C6/C7 haplotype analysis of South African C6-deficient (C6Q0) subjects revealed a strong allelic association of C6*Q0 and C7*M.

Alleles↗
PubMed1992

Antibodies to meningococcal class 1 outer membrane proteins in South African complement-deficient and complement-sufficient subjects.

Inhibition assays were used to investigate human serum antibodies to the meningococcal class 1 outer membrane proteins. We adapted the whole-cell enzyme-linked immunosorbent assay technique to determine the ability of sera to inhibit the binding of murine subtyping monoclonal antibodies. Serum samples from 33 South African subjects with a deficiency in the sixth component of complement as well as serum samples from various groups of complement-sufficient subjects were investigated. Subjects were subdivided according to whether they were (i) convalescent from Neisseria meningitidis infections, (ii) nonconvalescent, or (iii) controls. Preliminary subtyping investigations had shown that P1.2 was present on 36% of meningococcal clinical isolates from Cape Province, South Africa. Assays with the anti-P1.2 antibodies showed the presence of high antibody levels in many deficient sera and moderately elevated levels in some sera from the complement-sufficient convalescent patients. P1.2, P1.4, P1.15, and P1.16 are epitopes situated on loop 4 of the class 1 outer membrane proteins, whereas P1.7 is on loop 1. Inhibition assays showed that human sera that inhibited binding by P1.2 monoclonal antibodies tended to inhibit the other monoclonal antibodies directed to loop 4 epitopes. This suggests that the epitopes recognized by the human antibodies are not exactly the same as the epitopes recognized by the murine monoclonal antibodies and raises the possibility of the importance of other epitopes.

Antibodies, Bacterial↗
PubMed1992

Properties of a low molecular weight complement component C6 found in human subjects with subtotal C6 deficiency.

A sensitive ELISA assay was used to quantitate serum complement component C6 concentrations. Levels in the range 0.3-3 micrograms/ml were measured in samples from eight individuals (four separate pedigrees) and two subjects with subtotal combined C6/C7 deficiency who have been reported previously. We defined C6 levels in this range as subtotal C6 deficiency (C6SD). In contrast, C6 deficiency with levels below 0.03 micrograms/ml was defined as C6Q0. C6Q0 has been found in 29 unrelated cases which have already been reported. Investigations of the properties of the C6 found in the C6SD subjects showed it to be haemolytically active and able to incorporate into the terminal complement complex. The protein had a relative molecular weight (Mr) of approximately 86% of normal C6 and this Mr was identical to that of the C6 of one combined deficient subject. The Mr of the C6 of the other combined deficient subject was previously estimated as 79% of the Mr of normal C6. Isoelectric focusing (IEF) analysis with band development by haemolytic overlay revealed that all C6SD samples produced an identical weak C6 band pattern anodal to normal C6A bands. The C7 IEF patterns of the two combined deficient subjects were identical, and the C6 IEF patterns of both were identical to those of the C6SD subjects. Thus the C6 of the combined deficient subjects is probably the same abnormal protein found in the C6SD individuals. None of the C6SD or combined deficient subjects have had meningococcal disease and it may be that low C6 levels afford some protection.

Adult↗
PubMed1992

Inherited deficiencies of the terminal components of human complement.

The particularly frequent occurrence of terminal complement deficiencies in patients with Neisserial infections suggests that the cytolytic activity of the complement system is important in resistance to Neisseria meningitidis. There are, however, geographical differences in the prevalence of terminal complement deficiency in patients with meningococcal disease. The data available suggest that either recurrent infection or infection with uncommon serogroups should alert the clinician in Western countries whereas recurrent disease is the important indicator in high risk endemic or epidemic areas. An association of terminal complement deficiencies with susceptibility to autoimmune diseases or non-Neisserial infections is doubtful. For a better understanding of complement deficiencies in relation to disease more accurate characterization of the defects involved will be helpful. Sensitive ELISA techniques and molecular biological assays will be needed. Thus it has been established that two types of deficiencies exist (at least for C6, C7 and C8): one with low but detectable amounts of the component and the other with a complete absence of the protein in question. The subtotal variety appears to show less association with Neisserial infection. Low amounts of functional terminal complement activity may be sufficient for many of its biological functions, suggesting that there is a wide "safety margin".

Autoimmune Diseases↗
PubMed1991

Functionally active complement proteins C6 and C7 detected in C6- and C7-deficient individuals.

Two sensitive sandwich ELISAs based on monoclonal antibodies directed to native C6 and C7 allowed the detection and quantitation of these complement proteins in 20 out of 37 serum samples from individuals who had previously been classified as deficient in these proteins as assessed by immunochemical and/or functional assays. Furthermore, serum from four C6-deficient and one combined C6-/C7-deficient individual showed an increase in the terminal complement complex (TCC) and a decrease in native C6 and C7 after complement activation as assayed by specific ELISAs. Despite their (incomplete) deficiencies, these individuals therefore possess functionally active terminal complement proteins with respect to their ability to generate the TCC. As these individuals have no history of a susceptibility to neisserial infections, even low concentrations of functionally active C6 and C7 may provide sufficient protection against those micro-organisms whose destruction requires TCC formation.

Antibodies, Monoclonal↗
PubMed1990

Prophylaxis against Neisseria meningitidis infections and antibody responses in patients with deficiency of the sixth component of complement.

Forty South African patients with homozygous deficiency of the sixth component of complement (C6) have been identified in an area where group B meningococcal meningitis is endemic; 22 of the 24 proband cases presented with recurrent meningococcal meningitis. In a 2- to 4-year prospective study, patients with recurrent infections who received monthly prophylactic long-acting penicillin were significantly protected from subsequent neisserial infection compared with those who did not receive penicillin (P = .02, Fisher's exact test). Heterogeneous susceptibility to neisserial infection was confirmed by following C6-deficient patients who presented with one or no Neisseria meningitidis infections. These patients, on no prophylaxis, had significantly fewer infections (P = .004) than did patients who presented with recurrent disease. Functional C6 activity was restored by transfusion of fresh frozen plasma in a C6-deficient patient resistant to conventional antibiotic treatment. Antibody levels to the serotype 2 outer membrane proteins were significantly elevated in C6-deficient patients compared with control groups (P = .001).

Antibodies, Bacterial↗
PubMed1988

Allotypes of mouse complement component C6 in inbred strains and some wild populations.

This collaborative work was undertaken to resolve discrepancies in reports of the number of forms of complement component C6 present in the circulation of mice from various inbred strains. Plasma C6 was analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and by isoelectric focusing (IEF), and C6 band patterns were developed by electroblotting and immunoprobing. Results of C6 allotyping of mice from 36 strains confirmed that while 20 strains (prototype strain BALB/c) possessed only one relative mass (Mr) for which typed C6A1 on IEF, the other 16 strains all possessed more than one C6 Mr form. Moreover, IEF analysis demonstrated additional polymorphic differences; among these 16 strains, 11 typed C6A1B1 like the prototype strain CBA, the AKR and RF/J strains typed C6A2B2, and the Japanese MOM strain as well as the C57BR/cdJ and C57L/J strains possessed two forms with IEF mobilities intermediate between C6A1B1 and C6A2B2. These will now be referred to as C6A3B3. Thus, a total of four different mouse C6 haplotypes have been identified. Testing C6 allotypes in a limited number of wild mice revealed that haplotypes found in inbred strains of Western or Eastern origin tend to reflect haplotypes of the wild mice from Europe or Japan, respectively.

Animals↗
PubMed1987

Deficiency of the sixth component of complement and susceptibility to Neisseria meningitidis infections: studies in 10 families and five isolated cases.

Complement component C6 deficiency (C6D) was diagnosed in 15 patients who presented, independently, with recurrent meningococcal infection. This condition is thus not particularly rare in the Cape. Ten of the patients belonged to multiplex families, and family studies led to the diagnosis of another 12 C6D cases among the siblings. Segregation analysis showed that C6D occurred more frequently among the siblings of affected individuals than would be expected for co-dominant inheritance. The possible reasons for this are discussed. We also observed that the 12 non-proband C6D siblings included only four with a history suggestive of meningococcal infection, and thus C6D individuals apparently differ in susceptibility to Neisseria meningitidis infection. We confirmed previous observations that primary infection occurs later in C6D individuals than amongst susceptible complement-sufficient individuals. Among 123 patients presenting with primary meningitis, one case of C6D was diagnosed. The data show that C6D is an important factor associated with susceptibility to meningococcal infection in the Cape.

Adolescent↗
PubMed1985

Genetically determined molecular weight differences in murine complement component C6.

Plasma samples from male CBA, BALB/c and DBA/2 mice were subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Bands of C6 hemolytic activity in the washed resolving gel were identified by means of an erythrocyte/agarose overlay gel. CBA plasma was found to contain two forms of C6, one with a molecular weight (Mr) of approximately 90 000 (type A) and one with a Mr of 100 000 (type B); CBA mice were thus designated C6: A+B+. BALB/c and DBA/2 plasma on the other hand contained only the low molecular weight type A C6 and were designated C6: A+B-. Flat bed isoelectric focusing followed by functional overlays showed that CBA plasma produced two sets of hemolytic bands (pI 5.25-5.4 and 5.0-5.2) whereas BALB/c and DBA/2 plasma produced only the more cathodal band set. The additional band set in CBA plasma corresponded to the high-Mr type B C6. Results of breeding experiments demonstrated that the possession of the high Mr type B C6 was inherited in the manner of an autosomal phenotypically dominant characteristic.

Animals↗
PubMed1985

Close linkage between mouse genes determining the two forms of complement component C6 and component C7, and cis action of a C6 regulatory gene.

Two forms of mouse complement component C6, with molecular weights (Mrs) of 90 and 100 kilodaltons (kd), are present in the sera from certain inbred strains such as the CBA strain; other strains, such as the BALB/c and DBA/2 strains, have only the 90 kd C6A form. The present work was undertaken to determine whether the two Mr forms were the products of genes coding at separate loci. We screened sera from mice from a number of inbred strains by isoelectric focusing and found one strain, AKR, exhibiting allotypic structural variations of C6 forms. To distinguish the various types, we designated the 90 kd types from CBA and AKR mice C6A1 and C6A2, respectively, and the corresponding 100 kd types C6B1 and C6B2, respectively. Mice possessing only one Mr form were all typed as C6A1. Results of breeding experiments strongly suggested that the two Mr forms of C6 are coded for at two closely linked loci. Sera from a number of inbred strains were also screened for a complement C7 polymorphism by means of isoelectric focusing and functional overlay. C7 from all strains, excepting the AKR strain, produced identical C7 band patterns. AKR C7 produced a unique band pattern, and results of breeding experiments with AKR and BALB/c mice showed the C6 and C7 loci to be closely linked. In addition, we identified a regulatory gene for C6 production. The gene apparently requires androgen to facilitate C6 production in the majority of strains. In these strains C6 activity is virtually absent from female sera. However, we observed moderate levels of C6 activity in sera from IS/Cam females, indicating that, in this strain, male physiological androgen levels are not necessary for C6 production. IS/Cam possess one form of circulating C6 which appears identical with BALB/c C6A1, and therefore IS/Cam mice differ from AKR mice at both the C6 structural and regulatory loci. These two strains were thus suitable for use in breeding experiments to determine the manner of action of the regulatory gene. Results showed that it acted in a cis manner.

Animals↗
PubMed1985

HLA-A, B, C and DR antigen associations in insulin dependent diabetes mellitus (IDDM) in South African Negro (black) and Cape coloured people.

HLA-A, B, C and DR antigen frequencies were determined in South African Negro (Black) (50) and Cape Coloured (57) patients with insulin dependent diabetes mellitus (IDDM) and in appropriate controls. The Black patients failed to show associations commonly reported for American Black patients with IDDM but did show a weakly significant increase in the DRw9 frequency. However, this antigen was rare even in the patient group and HLA associated genes do not appear to play a major role in the pathogenesis of IDDM in these people. The Cape Coloureds have a high proportion of Caucasoid genes. Coloured IDDM patients had the expected low DR2 and high DR4 frequencies. Unexpectedly the Cape Coloureds failed to show significant associations of IDDM with B8 or DR3.

Adolescent↗