Biomedical subjects

L Beischel

Publications and source records attributed to L Beischel.

8 recordsLinked to original sources

PubMed1990

Functional consequences of the genetic polymorphism of the third component of complement.

The third component of complement, the central protein of the complement cascade, occurs in two principal allotypes, C3S and C3F. An excess frequency of the F allotype has been implicated in a number of disease states, including some forms of glomerulonephritis. These associations have been explained by functional differences between C3S and C3F. We examined several complement functions, using purified preparations of C3S or C3F. The C3S allotype was 1.3 times more efficient than C3F in a hemolytic assay employing sensitized sheep erythrocytes; this difference was shown to arise from a slightly more efficient deposition of C3F on the cell surface. These differences are trivial and of much less magnitude than the functional differences between C4A and C4B. There were no differences between allotypes in their ability to be converted to inactive C3b (C3bi) by complement factors H and I or by CR1 and factor I. No significant differences were seen between the allotypes and their ability to support solubilization of preformed immune complexes.

Animals↗

PubMed1988

Inhibition of immune complex solubilization by sera of patients with membranoproliferative glomerulonephritis.

Inhibition of complement mediated solubilization (CMS) of preformed immune complexes was previously demonstrated in the serum of patients with systemic lupus erythematosus. We studied the ability of serum from patients with MPGN I or III to inhibit the solubilization of preformed BSA- anti-BSA aggregates by pooled normal human serum. Inhibition of CMS was found in the sera of 20/35 patients; the inhibition was more dramatic in those with active disease (9/9), as compared to those in remission (8/21) or with renal failure (3/5). The inhibition did not seem to be related to corticosteroid therapy, nephrotic syndrome, circulating immune complexes or hypocomplementaemia. In only one patient was inhibition associated with the presence of C3 nephritic factor activity and decomplementation of the target serum.

Adolescent↗

PubMed1986

Major-histocompatibility-complex extended haplotypes in membranoproliferative glomerulonephritis.

Membranoproliferative glomerulonephritis is often associated with evidence of immune derangement, especially hypocomplementemia. We studied genetic markers for membranoproliferative glomerulonephritis within the major histocompatibility complex in 34 patients and their families and in 29 normal families. We examined the frequencies of extended haplotypes (combinations of alleles that tend to occur together) in patients and controls. The extended haplotype HLA-B8,DR3,SC01,GLO2(glyoxalase I 2) was observed in 9 of 68 disease-associated haplotypes (13 percent), but in only 3 of 205 controls (1 percent) (relative risk, 14.79; P less than 0.001). An extended haplotype similar except for a different glyoxalase allotype (B8,DR3,SC01,GLO1) did not occur with increased frequency, nor did any other extended haplotypes. Patients with the extended haplotype B8,DR3,SC01,GLO2 had a higher incidence of renal insufficiency than those without it (P less than 0.01). The data support the hypothesis that a specific extended haplotype of the major histocompatibility complex is associated with susceptibility to membranoproliferative glomerulonephritis, and that patients with glomerulonephritis who have this extended haplotype have a poorer prognosis for kidney survival than those without the haplotype.

Alleles↗

PubMed1986

IgA synthesis by lymphocytes from patients with IgA nephropathy and their relatives.

To investigate the hypothesis that a predisposition to IgA nephropathy (IgAN) is linked to the major histocompatibility complex (MHC) and associated with poorly regulated IgA synthesis, we performed HLA typing and lymphocyte cultures on patients with IgAN and their relatives. Nineteen of 22 patients had elevated culture supernatant IgA concentrations (620 vs. 154 ng/2 X 10(6) cells, P = 0.007). Supernatant IgG and IgM were normal. No HLA antigen occurred with increased frequency in patients. There was an increased incidence of homozygous null C4 alleles in patients (P less than 0.01). In families, six of 11 mothers, six of 12 fathers, and seven of 15 siblings had elevated supernatant IgA concentrations. There was no segregation of abnormal IgA production with any HLA antigen or parental haplotype. The data confirm elevated in vitro IgA production by lymphocytes from patients with IgAN, but do not support a linkage with the MHC. The increased incidence of homozygous null C4 alleles may result from functional differences in C4 A and B gene products. The familial clustering of elevated IgA production without an obvious inheritance pattern suggest that shared environmental factors may be important in the development of IgAN.

Alleles↗

PubMed1986

Relationship between the component and regulatory proteins of the classical pathway C3 convertase.

A relationship was found between the sums of the component proteins of the classical pathway C3 convertase (C2 and C4) and their regulators (C4bp and 1) in 184 normal controls. The relationship was maintained in most patients with low levels of individual components resulting from congenital deficiency and urinary losses, as well as in most cord sera. On the other hand, classical pathway activation in membranoproliferative glomerulonephritis type I, systemic lupus erythematosus, hereditary angioneurotic edema, and bacteremia resulted in loss of this relationship. Patients with alternative pathway-mediated complement activation (membranoproliferative glomerulonephritis type II) had a normal relationship between the classical component and regulatory proteins. In situations in which classical pathway activation is suspected, simultaneous examination of C4, C2, C4bp, and I may be helpful.

Angioedema↗

PubMed1985

C4 uremic variant: an acquired C4 allotype.

The major histocompatibility complex (MHC)-linked complotype region includes alleles for B, C2, and C4 loci. These loci are closely linked to each other and to HLA-DR on chromosome 6. The duplicated C4 loci, C4A and B, are especially polymorphic. In seven patients with renal insufficiency, we observed a C4 variant with electrophoretic mobility between C4B2 and C4B3. Four of these patients were detected during a study of MHC markers in membranoproliferative glomerulonephritis. Complete complotype and HLA data from families of five of the seven patients demonstrated that the variant was not inherited. The pattern was revealed by immunofixation electrophoresis and also by C4-specific hemolytic overlay. In serial plasma specimens taken from one patient, the C4 variant appeared only after the patient became uremic. However, the variant could not be produced in normal plasma after incubation with C4-depleted uremic plasma. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions of immunoprecipitated C4 from these patients showed C4A and C4B alpha chains of normal molecular mass; incompletely processed forms of C4 were not observed. We believe that this variant is probably acquired in the presence of uremia and may represent the C4B2.9 allele found by Wank and co-workers in many patients with glomerulonephritis. Family studies are mandatory to distinguish genetic variants from acquired alterations in the C4 phenotype.

Alleles↗

PubMed1985

The effect of null C4 alleles on complement function.

C4 is encoded at two polymorphic genetic loci (C4A and B), and "null" or unexpressed alleles are relatively common. An increased frequency of nulls has been reported in a variety of diseases. In the present study, C4 allotypes and C4 hemolytic efficiencies (the ratios of functional to antigenic levels) were determined for a population of 75 normal unrelated individuals. Of these, 28 had three gene products (single null at C4A or B) while three had no expressed C4A products and three had no C4B products (homozygous null). Mean antigenic C4 levels correlated with the number of expressed gene products but there was a wide spread of individual values. Those homozygous null for C4A had greater, and for C4B less, hemolytic efficiency than those with four gene products. However, there was no difference in the in vitro kinetics of C3 convertase formation between homozygous null C4A or C4B individuals. Therefore, the presence of null genes for C4 does not appear to compromise complement function sufficiently to account for the reported disease associations. Some of the associations may result from the fact that null genes for C4, as part of an extended HLA haplotype, may be genetically linked to disease susceptibility.

Adult↗

PubMed1985

A circulating inhibitor of fluid-phase amplification. C3 convertase formation in systemic lupus erythematosus.

C3 nephritic factor (C3NeF) was used to assess the formation of the fluid-phase amplification convertase, C3b,Bb, in 37 serum specimens from 24 patients with systemic lupus erythematosus (SLE). C3b,Bb formation was measured by the concentration of Ba, released when C3b,B is activated. Incubation of normal human serum (NHS) with C3NeF accelerates C3b amplification loop turnover with the formation of large quantities of C3b,Bb. In contrast, sera from 22 of 24 patients with SLE formed little or no convertase when incubated with C3NeF. C3 conversion to C3b was commensurately reduced. The inhibition could not be attributed to depressed serum concentrations of C3, factor B, or classical pathway components. Inhibitor present in excess could be demonstrated in 23 of 34 specimens of SLE serum by mixing experiments. The spontaneous convertase formation that occurs when a portion of the serum H is inactivated with F(ab')2 anti-H was also shown to be inhibited in SLE serum. The inhibition was found, however, to be H dependent in that convertase formation was normal in SLE serum depleted of H. It is concluded that the C3b in most SLE sera is unusually susceptible to inactivation by H, but a functional abnormality was not demonstrable in either C3 or H isolated from SLE serum. The inhibition could be simulated in NHS by addition of heparin, 100 micrograms/ml. In vivo, inhibition of convertase formation could interfere with the solubilization and disposal of immune complexes by reducing the deposition of C3b on the immune complex lattice.

Complement Activating Enzymes↗