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RELATION OF A beta(1)-GLYCOPROTEIN OF HUMAN SERUM TO THE COMPLEMENT SYSTEM

H J Müller-Eberhard1, U Nilsson

  • 1Department of Clinical Chemistry, University Hospital, Uppsala, Sweden.

The Journal of Experimental Medicine
|October 30, 2009
PubMed

Insights

Human beta(1C)-globulin, a complement system protein, converts to inactive beta(1A)-globulin upon activation by immune complexes or zymosan. This study investigates its role in complement activity and stability.

Area of Science:

  • Immunology
  • Biochemistry
  • Complement System

Background:

  • Human serum contains beta(1C)-globulin, a protein with serological activity linked to the complement system.
  • Beta(1A)-globulin is identified as the inactivated form of beta(1C)-globulin.
  • Complement activation involves complex interactions between serum proteins and activators like immune precipitates or zymosan.

Purpose of the Study:

  • To investigate the role of beta(1C)-globulin in the human complement system.
  • To characterize the conversion of beta(1C)-globulin to beta(1A)-globulin.
  • To assess the functional activity of purified beta(1C)-globulin and its interaction with complement components.

Main Methods:

  • Incubation of fresh human serum with immune precipitates, soluble gamma-globulin aggregates, or zymosan at specified temperatures.
  • Testing purified beta(1C)-globulin and beta(1A)-globulin for complement component activity using hemolytic assays.
  • Assessing the stability of isolated beta(1C)-globulin at 37°C and its effect on limited complement systems.

Main Results:

  • Beta(1C)-globulin was removed from serum upon incubation with immune precipitates or zymosan, converting to beta(1A)-globulin.
  • Purified beta(1C)-globulin reconstituted hemolytic activity in guinea pig R(3) but not human R(3); beta(1A)-globulin was inactive.
  • Isolated beta(1C)-globulin lost activity and converted to beta(1A)-globulin upon storage at 37°C; it enhanced complement-mediated hemolysis and stabilized EAC'(1, 4, 2).

Conclusions:

  • Beta(1C)-globulin is an active component of the complement system, undergoing conversion to an inactive form (beta(1A)-globulin) upon activation.
  • The study provides evidence for the functional role of beta(1C)-globulin in complement-mediated hemolysis and stabilization of immune complexes.
  • Beta(1C)-globulin's instability at physiological temperatures contributes to its transient activity in the complement cascade.

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