R F Dyck

AMYLOID P-COMPONENT IN HUMAN GLOMERULAR BASEMENT MEMBRANE: Abnormal Patterns of Immunofluorescent Staining in Glomerular Disease

Serum amyloid P-component (SAP) is a normal plasma protein and is a constituent of normal human glomerular basement membrane. Immunofluorescence with anti-SAP antibody produced characteristic linear staining along the glomerular basement membrane in normal kidney. Distinctive abnormal staining patterns were seen in renal biopsy specimens from patients with diabetes, membranous glomerulonephritis, mesangiocapillary nephritis, systemic vasculitis, Goodpastures syndrome.

Solid-phase immunoradiometric assay for serum amyloid A protein using magnetisable cellulose particles.

An immunoradiometric assay for human serum amyloid A protein (SAA) was developed using magnetisable cellulose particles as the solid phase. Rabbit antiserum to to SAA was raised by immunization with SAA isolated from acute-phase serum by gel filtration in formic acid. The antiserum was rendered monospecific for SAA by solid-phase immunoabsorption with normal human serum, which contains only traces of SAA, and some was coupled covalently to the cellulose particles. Immunopurified anti-SAA antibodies were isolated from the monospecific anti-SAA serum by binding to, and elution from insolubilized acute-phase serum and were radiolabelled with 125I. The assay was calibrated with an acute phase serum which contained 6000 times more SAA than normal sera with the lowest detectable level of SAA, and an arbitrary value of 6000 U/l was assigned to this standard. Sera were tested in the native, undenatured state and there was no increase in SAA immunoreactivity following alkali treatment or heating. The assay range was from 1-2000 U/l so that all SAA levels above 6 U/l could be measured on a single (1:6) dilution of serum. The intra- and interassay coefficients of variation were 11.7 and 15.0% respectively. Among 100 healthy normal subjects (50 male, 50 female) the median SAA level was 9 U/l, range less than 1-100, with 93% below 20 U/l and only 2% below the lower limit of sensitivity of the assay (1 U/l).

Studies of human serum amyloid P-component (sap) in relation to coagulation

Abstract Serum amyloid P-component (SAP) undergoes calcium-dependent binding to certain polysaccharides and polyanions. It has been claimed that it acts as a heparin antagonist and that plasma SAP levels are low in patients treated with vitamin K antagonist anti-coagulant drugs. However, in the present study depletion of SAP from plasma had no effect on subsequent coagulation, indicating that it is not a necessary procoagulant. SAP levels in male patients receiving warfarin were the same as in normal controls; in a group of female patients on warfarin, SAP levels were slightly higher than normal, probably in response to the underlying condition for which they were anticoagulated. The SAP from warfarin-treated individuals was indistinguishable from normal SAP antigenically, electrophoretically and in its calcium-dependent ligand binding. Isolated SAP did not inhibit the anti-coagulant activity of heparin, on the contrary, addition of supraphysiological amounts of isolated SAP to citrated plasma or to mixtures of fibrinogen and thrombin inhibited clotting, possibly by interfering with fibrin polymerisation. C-reactive protein (CRP), the classical acute phase reactant, which is closely related to SAP, did interfere with the neutralisation of factor Xa by heparin. This effect was produced by concentrations of CRP within the range commonly seen in disease states, suggesting that it may be the counterpart of an in vivo role for CRP in the acute phase response.