A new BF F variant by polyacrylamide gel isoelectric focusing

Summary Polyacrylamide gel isoelectric focusing followed by electroblotting with enzyme immunoassay was done for the investigation of allotypes of properdin factor B (BF) in serum from 326 Japanese subjects. A new BF F variant tentatively designated BF*Fb1 (b=basic) was detected, the isoelectric point of each band of homozygous BF Fb1 being higher than of BF FF. Family data were in accordance with transmission by mendelian inheritance. The allele frequencies calculated from 326 Japanese subjects were 0.7945, 0.1825, 0.0215, and 0.0015 for BF*S, BF*F, BF*Fb1, and BF*F075, respectively, with that of variant BF*Fb1 being a polymorphic frequency. The distribution of phenotypes fitted the Hardy-Weinberg equilibrium.     

A new BF variant (F025)

A rare variant of Factor B exhibiting a mobility intermediate between BF F and BF S was described. After comparison with the mobilities of BF F and F075, this variant was designated BF F025. The allele was transmitted together with C2*C, C4A*3, and C4B*1.     

An unusual "morphologic" variant of BF S

In the course of family studies of haplotypes of the alleles of the sixth chromosome loci HLA-A, C, B, D/DR, BF, C2, C4A, C4B, and glyoxalase I, we encountered an unusual BF variant. Its mobility was similar to BF F but it appeared to have a lesser intensity after straining with Coomassie Blue, and it was demonstrated by crossed immunoelectrophoresis to be present in lower concentration. It was therefore designated BF FQL. This variant was found on the haplotype HLA-A1, B17, DR7, BF*FQL, C2*C, C4A*6, C4B*1, GLO2. All other haplotypes of this type so far identified carry the BF variant BF S. Following activation of serum samples with zymosan, BF was analyzed by both agarose electrophoresis and isoelectric focusing and immunofixation. On both treatments, serum with BF SFQL produced a Ba pattern identical to that of a sample which was BF S. The Bb pattern for F and S are similar but differ from those of the rare variants BF F1 and BF S1. The Bb pattern of BF FQL was, thus, as expected, the same as BF F or BF S. Hence, we conclude that the variant is a mutant from BF S with mobility similar to BF F. The mutation seemed also to have resulted in a lower concentration of product than normal.     

Polymorphisms of serum proteins in Japanese patients with vascular diseases. I. Factor XIIIB, plasminogen and complement types in primary varicose veins.

The polymorphisms of the B subunit of coagulation factor XIII (F13B), plasminogen (PLG), complement C6, C7, factor B (BF) and factor I (IF) were studied among 21 unrelated Japanese patients with primary varicose veins (PVV) by isoelectric focusing followed by immunoblotting. The allele frequencies for F13B*2 and IF*A in PVV patients were significantly higher (F13B*2, p = 0.0047; IF*A, p = 0.0006) than those in healthy controls (n = 60). Significant associations of F13B 2 allotype [p = 0.0220, relative risk (RR) = 13.9] and IF A allotype (p = 0.0006, RR = 10.0) with PVV were observed; however, no significant association of PLG, C6, C7 or BF allotype with the disease was found.     

中国广州人备解素因子B遗传多态现象

本文应用高压琼脂糖电泳,继以免疫固定技术,对259名居住在广州市无亲缘关系的健康成年人进行了BF多态性分析。除了SS、FS、FF和SS07外,还观察到2种罕见杂合型,暂命名为SSGI和SFG2。计算出的基因频率分别为:FB~*S∶0.8668,BF~*F∶0.11979 BF~*S07∶0.0077,BF~*SG1∶0.0019,BF~*FG2∶0.0039。家系调查证实BF FG2确系一独立的变异型,并显示常染色体共显性遗传方式。     

Identification of HLA-B44 subtypes associated with extended MHC haplotypes

The HLA class I antigen B44 is found in each of two different extended major histocompatibility haplotypes (allele combinations of HLA-B, HLA-DR, and complement genes BF, C2, C4A, and C4B in linkage disequilibrium). Using isoelectric focusing, two variants of HLA-B44 were identified. The basic variant was found in all cell lines with the extended haplotype HLA-B44, DR7, FC31, and the acidic variant in all cell lines with the extended haplotype HLA-B44, DR4, SC30. The occurrence of each antigen variant with a unique extended haplotype explains previous observations concerning the nonrandom association of B44 variants with DR antigens.     

BF types and the mode of inheritance of insulin-dependent diabetes mellitus (IDDM)

Insulin-dependent diabetes mellitus (IDDM) has been found to be highly associated with a rare allele of the complement protein, properdin factor B (BF). Assuming that there is a susceptibility gene for IDDM tightly linked to the genetic locus forBF and the major histocompatibility complex (MHC), the distribution of BF types in more than 1100 North American IDDM patients strongly argues for the rejection of dominant, epistatic, and overdominant modes of inheritance. Other evidence suggesting complex modes of inheritance for IDDM is reviewed and it is concluded that our observations and published data are consistent with the idea of susceptibility to IDDM being inherited as a simple autosomal recessive trait. — C4 and C2 types, also linked toBF and theMHC, were investigated too. C4 Fs⁰ was found to be increased in association with BF F1, while C4 f⁰S and C2 B were each found to occur twice as frequently as in a control population and will be of value in defining haplotypes associated with susceptibility to IDDM.     

Properdin factor B frequencies in four Asian populations

The distribution of Properdin factor B (Bf) phenotypes and their gene frequencies were investigated in four Asian populations (Chinese, Filipino, Thai and Japanese). The frequency of the BfS phenotype in Filipinos (0.717) was significantly lower than that in Chinese (0.900) and Thai (0.889) (p less than 0.01), but not different from the Japanese (0.840). One variant, BfF 0.65 S, was identified in a Japanese subject. Thus, in the Asian populations studied, Bfs frequencies were high and the frequency of variants other than F and S were low.     

Polymorphism of BF,C2, and GLO in Japanese patients with insulin-dependent diabetes mellitus: Confirmation of an increase of BF *FT

Summary The distribution of phenotypes controlled by three HLA-linked loci BF, C2, and GLO has been studied in Japanese patients with insulin-dependent diabetes mellitus (IDDM). A slight but significant higher incidence of a rare varian BF ^*FT (=^* F075) in patients was confirmed in the combined data with our previous study (Tokunaga et al. 1981 b). No significant association of C2 and GLO alleles with IDDM was found.     

Bf polymorphism. A very fast variant from Nigeria

Summary In a collection of Nigerian serum samples typed for alleles of factor B of the alternative complement pathway, a very high frequency of Bf^F was found (0.69). In addition, a new variant was found in two samples. This variant (F^1.29) moved faster than BfF₁. It was hemolytically active.Supported in part by The Medical Research Council of Canada     

Apparently non-expressed alleles of factor B (BF) code for hypomorphic proteins

In three families with an apparent non-expressed factor B (BF) allele (BF ^* Q0), advanced methods of isoelectric focusing for the determination of BF F subtypes revealed different hypomorphic BF products (BF QL) with functional hemolytic activity expressed by the assumed BF ^* Q0 allele. A Taq I and a Msp I restriction fragment length polymorphism as well as the Ba fragment of the expression products showed banding patters for the BF ^* QL alleles corresponding to BF S types, whereas an altered Bb fragment was seen in two BF QL products. In one family an intragenic recombination site within the Bb part of the BF gene was assumed. Investigations of factor B and its conversion fragments, as demonstrated by the used methods, allow to complement molecular genetic investigations of BF ^* Q0 alleles in heterozygous genotypes on a protein level. We conclude that apparently non-expressed alleles of factor B code for hypomorphic but functionally active proteins. Correspondence to : I. Siemens.     

Further study on a BF silent allele

Summary A family was found which indicated the existence of a silent allele (BF ^* QO) at the locus for complement factor B. Three generations with eight members were studied. Four individuals were considered to be heterozygous for B deficiency because of unusual segregation patters of the BF electrophoretic variants and low levels of B. Haplotype study on the other HLA-linked markers supported the presumption. No unusual products were detected by immunoblotting after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).     

Another family with a silent allele of properdin factor B polymorphism (BF*QO)

Summary In five of eight members of a three generation family the existence of a silent allele of the properdin factor B polymorphism (BF^*QO) was indicated by immunofixation of BF electrophoretic variants and by the hemolytic overlay after isoelectric focusing of BF allotypes. This was further supported by the results of HLA-A, B, C, DR, C2, C4A, C4B, GLO-typing. BF protein was decreased in all heterozygous BF deficient family members. The absolute hemolytic activity, however, was obviously compensated for by an increased relative functional activity of the normal S or F alleles on the other chromosome.     

PGD variants in several wild pig populations of East Asia

PGD (6-phosphogluconate dehydrogenase) gene frequencies were reported in wild pigs, Sus scrofa, of three subspecies, i.e. Japanese wild pig, S.s. leucomystax, Ryukyu wild pig, S.s. riukiuanus, and Formosan wild pig, S.s. taivanus. Five phenotypes (A, AB, B, AC' and C') were observed. The C' variant was found only in the S.s. leucomystax, and may be identical to PGD-C reported by Archibald & McTeir (1988). PGD-A was a common variant in all the species in the genus Sus including wild pig, Sus scrofa, Javan pig, Sus verrucosus, and Bearded pig, Sus barbatus, and predominated in the whole populations examined except some of those of the S.s. riukiuanus. This suggested that the PGDA appeared before the other two alleles (B and C') during the evolution of the genus Sus.     

Polymorphism of MHC class III genes: definition of restriction fragment linkage groups and evidence for frequent deletions and duplications

Summary The loci for the complement proteins BF and C2 and the two loci for C4 are closely linked to one another, as are the duplicated steroid 21 hydroxylase (21-OHase) genes to the C4A and C4B loci. The alleles of these four loci occur in specific combinations termed complotypes. We have studied the gene frequencies of their different products in the Lebanese population and compared these values with those found in other populations. We observed a novel complotype (S B 4 6) in one family and a complotype with a so far undescribed variant of the C4A locus. Using several restriction fragment length polymorphisms (RFLPs), we have defined restriction fragment linkage groups. The combined use of C4 and 21-OHase probes allowed us to detect different types of deletions and duplications at these loci in the Lebanese population.     

C4 allotyping distinguishes HLA-1314.1 and B14.2 subgroups

Complement allotyping (C4, C2, and BF) was performed in 60 unrelated individuals and 15 families characterized for the subtypes (14.1 and 14.2) within HLA-B14. Eighty-seven percent of B14.2 individuals typed positive for the rare C4A2 variant. In contrast, less than 7% of B14.1 individuals were positive for this C4 allotype which is in keeping with a control background frequency. Family studies revealed that three distinct complotypes (complement haplotypes) are characteristic for the two HLA-1314 subgroups. The SC22 and FC31 complotypes characterize the B14.2 subtype, whereas SC31 appears to define B14.1.     

Allelic differences in hemolytic activity and protein concentration of BF molecules are found in association with particular HLA haplotypes

After separating the *F and *S alleles by electrophoresis the allele-specific hemolytic activity was detected by agarose overlay method using the programmable densitometer for scanning. The hemolytic activity of BF allotypes was analyzed from 81 individuals. In thirteen FS heterozygous serum samples BF F had lower hemolysis than BF S. Four FF homozygous samples also exhibited lower hemolysis than a homozygous control sample. The low hemolytic activity of F in FS heterozygotes was not due to decreased protein concentrations relative to S. On the contrary, BF F was associated with higher protein concentration than BF S. The relative quantitation of the allele specific BF protein was done by crossed immunoelectrophoresis. BF F with low hemolytic activity but with high protein concentration associated strongly with HLA B35 phenotype and the family material confirmed the association with the haplotypes A3, Cw4, B35, DR1, BFFB, C4A3BQO (or A2BQO, A3,2BQO). The results suggest that particular MHC haplotypes contain a factor B allele with encoding for poor hemolytic activity or that MHC haplotype specific regulatory elements affect pre- or post-translational activity levels.     

Conservation of the RD-BF-C2 organization in the pig MHC class-III region: mapping and cloning of the pig RD gene

The RD gene, named after the arginine (R) and aspartic acid (D) repeat in the central part of its protein, was initially mapped in the mouse H-2S subregion between C4 and BF. It was later mapped in the same position in the human MHC and here we show it is also conserved in the pig MHC class III region, close to the complement BF gene. A pig RD genomic clone was isolated from a γ-phage library. Hybridizations on genomic DNA separated with pulsed field gel electrophoresis identified common 220kb Nrul, 130 kb EagI and 200 kb Mlul bands for RD, BF and C2. The RD gene has also a 17 kb Kpnl and 11 kb Sad fragment in common with BFbut not with C2. The close linkage of the RD and BF genes was further established by hybridization of BF to a genomic γ-phage clone also containing the RD gene. This genomic RD clone overlaps with a γ -phage clone previously isolated and containing the complete BF gene and the 3' part of C2. The distance between RD and BF is about 6 kb. The junction between the two complement genes BF and C2 was sequenced and the BF 5' promoter region, overlapping the 3' noncoding region of C2, was compared with that of the human BF promoter. The overall homology was about 80% and all but one identified promoter elements were found in the same position in both genes. The results obtained demonstrate the RD-BF-C2 organization is strongly conserved between human, mouse and pig. No polymorphisms were detected in either the RD gene or in the BF promoter region using polymerase chain reaction and restriction fragment polymorphism analysis.     

MHC-linked class III genes. Analysis of C4 gene frequencies,complotypes and associations with distinct HLA haplotypes in German Caucasians

The class III complement components, C4, C2 and factor B (BF), are encoded in the human major histocompatibility complex (MHC). The two genes determining C4 (C4A and C4B) display considerable polymorphism and, thus, are important markers for HLA. In combination with alleles of C2 and BF they can be grouped into unique complotypes. We have analyzed the C4 alleles in a panel of 204 unrelated German Caucasians and studied their segregation with HLA haplotypes in 24 normal families. Inclusion of the class III markers with the class I and 11 alleles provides a more refined picture of the genetic structure of the MHC in these families. When charted according to the HLA-B locus specificities the MHCs can be clustered into groups showing distinctly homogenous or heterogenous complotypes. The identification of such groups is valuable for the selection of genetic material to analyze the molecular genetics of the human MHC.Abbreviations BF factor B - C2 second component of complement - C4 fourth component of complement - EDTA ethylenediamine tetraacetate - GLO glyoxalase-I - MHC major histocompatibility complex     

Association of C3 and C4A complement types with familial amyloidotic polyneuropathy

A mutant variant of the serum protein transthyretin (TTR-met30) appears to be a necessary but not sufficient condition for the development of familial amyloidotic polyneuropathy (FAP). We have studied a number of serum protein markers (alpha 1-antitrypsin, properdin factor B, C3, C4A, C4B, haptoglobin, transferrin and group-specific component) in FAP patients and healthy controls in an attempt to identify additional pathogenic factors which may influence the risk for developing FAP in male and female patients as well as the age of onset of the disease. Statistically significant associations were found in the complement systems C3 and C4A. The C3F variant was significantly increased in all FAP patients with a relative risk (RR) of 2.0, more pronounced in female patients (RR = 2.6) and patients with an early onset of the disease (RR = 4.5). In the FAP patients only the variants A3 and A4 were found in the C4A system. C4A3 was found in all patients, which was significantly higher than in the controls. The remaining serum protein systems showed no statistically significant associations with FAP. The results suggest that genetic variants of complement factors C3 and C4A may interact with the mutant TTR-met30 by modifying the expression and onset of FAP.