Hereditary and acquired deficiencies of C1 inhibitor

Area of Science:

• Immunology
• Biochemistry
• Genetics

Background:

• Angioneurotic edema is linked to deficiencies in C1 inhibitor (C1 INH), a crucial protease inhibitor.
• C1 INH regulates complement, kallikrein, and coagulation pathways.
• It is the most heavily glycosylated plasma protein, with O-linked carbohydrates.

Purpose of the Study:

• To define the molecular genetic defects in the C1 inhibitor gene.
• To understand the mechanisms behind hereditary and acquired angioneurotic edema.

Main Methods:

• Analysis of C1 inhibitor (C1 INH) structure and function.
• Molecular genetic studies of C1 INH gene defects.
• Characterization of C1 INH autoantibodies in acquired forms.

Main Results:

• Hereditary angioneurotic edema (HANE) involves heterozygous C1 INH deficiency (absolute or dysfunctional).
• Acquired angioneurotic edema (AANE) is associated with B-cell lymphoproliferative disorders or autoantibodies against C1 INH.
• Molecular genetic defects in HANE types 1 and 2 are being elucidated.

Conclusions:

• C1 INH deficiency is the central cause of angioneurotic edema.
• Both genetic and acquired forms have distinct underlying mechanisms.
• Further research is defining the genetic basis and identifying autoantibodies.