C4 concentrations and C4 deficiency alleles in systemic lupus erythematosus

Article Abstract:

The body's natural defense system, the immune system, consists of cells and factors that inactivate foreign substances called antigens. In the presence of an antigen, certain types of immune cells produce specialized proteins called antibodies that specifically bind with and inactivate the antigen. Under abnormal conditions, cells and factors of the immune system attack body tissues and natural substances in what is called the autoimmune response. Systemic lupus erythematosus (SLE), a chronic inflammatory disease of connective tissue, is thought to be an autoimmune disease. SLE is characterized by the formation of immune complexes consisting of antigens bound to antibodies, and a reduction in complement proteins which are involved in various immune defense mechanisms. The blood levels of the C4 complement protein are used to monitor disease activity. C4 consists of two forms, C4A and C4B, which are coded by genes located at different sites on the chromosome, a threadlike structure in the nucleus. In 60 to 80 percent of SLE patients, certain pairs of genes called null alleles fail to code for proteins and may affect C4 protein levels. Among 66 SLE patients and 80 normal subjects, it was found that the presence of two null alleles had a significant effect on C4 levels. The C4 levels were 56 percent lower in six normal subjects with two C4 null alleles when compared with the 43 normal subjects, and 55 percent lower in four SLE patients when compared with the 32 SLE patients without null alleles. Thus, the presence of null alleles appears to influence the levels of C4 in patients with SLE. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Measurement, Complement (Immunology)

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A study of the association of HLA DR, DQ, and complement C4 alleles with systemic lupus erythematosus in Iceland

Article Abstract:

A genetic complement deficiency may influence the risk of developing systemic lupus erythematosus (SLE) and the progression of the autoimmune disease. The complement protein system contributes to and modulates immune system responses to potentially foreign cell membranes. Researchers compared 64 SLE patients and 64 healthy volunteers in Iceland. Null, or nonfunctioning, genes for the complement protein C4 were more common in SLE patients. This complement deficiency may result in the inadequate clearance of immune system products, increasing the destruction of tissues.

HLA histocompatibility antigens, HLA antigens, Genetic polymorphisms

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Differential contribution of HLA-DR, DQ, and TAP2 alleles to systemic lupus erythematosus susceptibility in Spanish patients: role of TAP2*01 alleles in Ro autoantibody production

Article Abstract:

Particular genes may be associated with increased risk and severity of systemic lupus erythematosus (SLE) in Spanish people. SLE is an autoimmune disease. Researchers in Spain compared genetic profiles of 85 people with SLE and 186 healthy volunteers. Particular human leukocyte antigen (HLA) genes were more common in SLE patients, and associated with kidney damage from the disease. The genes which related to SLE in Spanish patients were different than those associated with the disease in other ethnic groups.

Spaniards, HLA class II antigens

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