Biomaterial Database

Molecular genetics of the fourth component of human complement. 1986

M C Carroll, and A Palsdottir, and K T Belt, and C Y Yu

The fourth component of human complement is encoded by two separate, but closely linked, loci, C4A and C4B, that have been positioned within the class III region of the HLA complex. While the two isotypes vary by only six amino acid residues, they differ significantly in haemolytic activity. Both loci are considerably polymorphic and this may be biologically relevant to ensure interaction with a wide range of pathogens. The number of C4 genes expressed is polymorphic as null alleles, total deficiency and duplication has been shown based on protein studies. Southern analysis of 24 different haplotypes with either C4A or C4B null alleles using the C4 probes showed that three of the null alleles were due to deleted genes but the majority appeared normal. A cosmid library was prepared from DNA of one of the deleted haplotypes and the region of deletion analysed by restriction mapping.

UI	MeSH Term	Description	Entries
D011110	Polymorphism, Genetic	The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.	Gene Polymorphism,Genetic Polymorphism,Polymorphism (Genetics),Genetic Polymorphisms,Gene Polymorphisms,Polymorphism, Gene,Polymorphisms (Genetics),Polymorphisms, Gene,Polymorphisms, Genetic
D002872	Chromosome Deletion	Actual loss of portion of a chromosome.	Monosomy, Partial,Partial Monosomy,Deletion, Chromosome,Deletions, Chromosome,Monosomies, Partial,Partial Monosomies
D002874	Chromosome Mapping	Any method used for determining the location of and relative distances between genes on a chromosome.	Gene Mapping,Linkage Mapping,Genome Mapping,Chromosome Mappings,Gene Mappings,Genome Mappings,Linkage Mappings,Mapping, Chromosome,Mapping, Gene,Mapping, Genome,Mapping, Linkage,Mappings, Chromosome,Mappings, Gene,Mappings, Genome,Mappings, Linkage
D003181	Complement C4	A glycoprotein that is important in the activation of CLASSICAL COMPLEMENT PATHWAY. C4 is cleaved by the activated COMPLEMENT C1S into COMPLEMENT C4A and COMPLEMENT C4B.	C4 Complement,C4 Complement Component,Complement 4,Complement C4, Precursor,Complement Component 4,Pro-C4,Pro-complement 4,C4, Complement,Complement Component, C4,Complement, C4,Component 4, Complement,Component, C4 Complement,Pro C4,Pro complement 4
D005802	Genes, MHC Class II	Genetic loci in the vertebrate major histocompatibility complex that encode polymorphic products which control the immune response to specific antigens. The genes are found in the HLA-D region in humans and include H-2M, I-A, and I-E loci in mice.	Class II Genes,Genes, Class II,Genes, HLA Class II,MHC Class II Genes,Class II Gene,Gene, Class II
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000483	Alleles	Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.	Allelomorphs,Allele,Allelomorph
D015934	Complement C4a	The smaller fragment formed when complement C4 is cleaved by COMPLEMENT C1S. It is an anaphylatoxin that causes symptoms of immediate hypersensitivity (HYPERSENSITIVITY, IMMEDIATE) but its activity is weaker than that of COMPLEMENT C3A or COMPLEMENT C5A.	C4a Complement,Complement 4a,Complement Component 4a,C4a, Complement,Complement, C4a,Component 4a, Complement
D015935	Complement C4b	The large fragment formed when COMPLEMENT C4 is cleaved by COMPLEMENT C1S. The membrane-bound C4b binds COMPLEMENT C2A, a SERINE PROTEASE, to form C4b2a (CLASSICAL PATHWAY C3 CONVERTASE) and subsequent C4b2a3b (CLASSICAL PATHWAY C5 CONVERTASE).	C4b Complement,Complement 4b,Complement Component 4b,C4b, Complement,Complement, C4b,Component 4b, Complement