Identification of four subpopulations of IgG anticardiolipin antibodies in patients with primary antiphospholipid syndrome on the basis of their requirement for beta 2-glycoprotein-I and their unmasking by heat.
Heat-treatment of normal human serum (NHS) results in positive seroconversion of IgG anticardiolipin antibodies (aCL) that do not depend on beta 2-glycoprotein-I (beta 2GP-I) for their detection in vitro as do some IgG aCL from patients with primary antiphospholipid syndrome (PAPS). Other IgC aCL from PAPS depend on beta 2GP-I for phospholipid binding. Here, we studied heat-unmasked aCL from 22 PAPS sera and from eight normal individuals. IgG aCL were detected in standard (using new born calf serum [NBCS] that contains beta 2GP-I as blocking agent and to dilute samples) and in a modified ELISA (using beta 2GP-I-free-bovine serum albumin instead of NBCS). Overt and heat-unmasked IgC aCL were purified from CL micelles alone or mixed with purified beta 2GP-I. NHS had no overt IgG aCL. In contrast, aCL titers increased almost ten-fold after heat-inactivation of NHS, a result which was equally detectable in both assay conditions. As expected, PAPS patients had one population of overt beta 2GP-I-dependent IgG aCL. After heat-treatment of all PAPS sera, we detected IgG aCL in both standard and modified aCL ELISA with an approximately three-fold increase in IgG aCL titers when tested in the standard assay. Two PAPS patients also had a second population of beta 2GP-I-independent overt IgG aCL. Purified IgG from these PAPS sera retained both reactivities.(ABSTRACT TRUNCATED AT 250 WORDS)
Cabiedes
J
J
Department of Immunology and Rheumatology, Instituto Nacional de la Nutrición Salvador Zubirán, Mexico D.F., Mexico.
Cabral
A R
AR
Alarcon-Segovia
D
D
D017153:Antibodies, Anticardiolipin / Q000032:analysis* / Q000145:classification*; D016736:Antiphospholipid Syndrome / Q000276:immunology*; D001053:Apolipoproteins / Q000502:physiology; D006023:Glycoproteins / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis*; D053482:beta 2-Glycoprotein I
D017153:Antibodies, Anticardiolipin; D001053:Apolipoproteins; D006023:Glycoproteins; D007074:Immunoglobulin G; D053482:beta 2-Glycoprotein I