Free protein S levels are elevated in familial C4b-binding protein
deficiency
PC Comp, J Forristall, CD West and RG Trapp
Department of Medicine, University of Oklahoma Health Sciences Center,
Oklahoma City 73104.
In plasma, 40% of the protein S is free and functions as a cofactor for the
anticoagulant effects of activated protein C. The remaining 60% of protein
S is complexed to C4b-binding protein and is functionally inactive. A
family with hereditary C4b binding protein deficiency has been identified
with C4b-binding protein levels in an affected father and daughter of 37
micrograms/mL and 23 micrograms/mL, respectively; these values are
significantly below the normal range for this protein of 180 micrograms/mL
+/- 44 micrograms/mL (mean +/- 2 SD). The total protein S (free + bound) is
normal in these individuals (23.2 micrograms/mL and 17.8 micrograms/mL,
respectively; normal 19.1 micrograms/mL +/- 6.0 micrograms/mL). The free
protein S levels are markedly increased at 22.5 micrograms/mL and 17.4
micrograms/mL, respectively (normal 5.9 micrograms/mL +/- 2.4
micrograms/mL). This experiment of nature shows that total protein S levels
in plasma are not affected by the absence of C4b-binding protein and that
chronic elevation of free protein S is not associated with increased
hemorrhagic tendencies.
Volume 76,
Issue 12,
pp. 2527-2529,
12/15/1990
Copyright © 1990 by The American Society of Hematology
