Genetic polymorphism of human factor I (C3b inactivator)

Area of Science:

• Human genetics
• Immunology
• Biochemistry

Background:

• Human factor I (C3b inactivator) plays a crucial role in regulating the complement system, a key part of innate immunity.
• Understanding genetic variations in factor I is important for studying its function and potential associations with diseases.

Purpose of the Study:

• To investigate the genetic polymorphism of human factor I.
• To determine the inheritance pattern and allele frequencies of human factor I genetic variants.

Main Methods:

• Polyacrylamide gel isoelectric focusing electrophoresis of neuraminidase-treated EDTA plasma samples.
• Electrophoretic blotting technique for genetic typing.
• Analysis of family material to confirm inheritance patterns.

Main Results:

• Three common phenotypes were observed in 435 individuals, controlled by two common alleles (FI*B and FI*A) at a single locus.
• Autosomal codominant Mendelian inheritance was confirmed.
• Gene frequencies were estimated as FI*B = 0.8931 and FI*A = 0.1069, with phenotype distribution fitting Hardy-Weinberg equilibrium.

Conclusions:

• The genetic polymorphism of human factor I is well-defined with two common alleles and follows predictable inheritance.
• No close linkage was found between factor I and the major histocompatibility complex, suggesting independent assortment.