PubMed · 8135461
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G Gambaro, A Ruffatti, A Antonello. 1994-04-15. Primary selective IgA deficiency.. https://doi.org/10.7326/0003-4819-120-8-199404150-00022
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Autoantibodies targeting beta2-glycoprotein l (beta2-GPI), a component of the atherosclerotic plaque, are commonly found in patients with acute ischemic syndromes. Serum samples from APS (antiphospholipid syndrome) patients and from cardiovascular patients exhibiting acute atherosclerotic syndromes were analyzed for IgG and IgA antibodies in both anti-beta2-GPI and anticardiolipin (aCL) ELISA assays. All of the APS samples used here were positive in both assays. Serum samples from 382 atherosclerosis patients were also analyzed for IgG and IgA antibodies in the same assays. In sharp contrast to the APS samples, we found that only 1% of the samples from atherosclerosis patients were positive for IgA aCL, and 1.6% positive for IgG aCL, whereas 35.6% were positive for IgA anti-beta2-GPI and only 1.6% for IgG anti-beta2-GPI. The antigenic specificity of 29 serum samples from atherosclerosis patients was evaluated. Six different recombinant domain-deleted mutants (DM) of human beta2-GPI and full-length human beta2-GPI (wild-type) were used in competitive inhibition assays to inhibit the autoantibodies from binding in the anti-beta2-GPI ELISA assays. Domain-deleted mutants D--345 and D--45 inhibited the binding in the IgA anti-beta2-GPI assay, suggesting that these autoantibodies recognize domain 4 of the beta2-GPI molecule. These results clearly show that IgA anti-beta2-GPI autoantibodies from atherosclerotic patients are distinct from IgA autoantibodies found in APS samples.
Lupus anticoagulant (LA) and anticardiolipin (aCL) antibodies are the classical tests used to diagnose the antiphospholipid syndrome (APS). Unfortunately, since these are nonspecific and standardization is lacking, the results of laboratory work-ups upon which diagnosis are made are often misleading. The performance of clinical laboratories in detecting LA using lyophilised affinity purified immunoglobulin has been previously reported. The same material was used to investigate the inter-laboratory variability of aCL and anti-beta(2)-Glycoprotein I (beta(2)-GPI) antibody measurements. Laboratories were asked to test normal plasma spiked with purified IgG or distilled water in order to obtain 3 samples positive for aCL and anti-beta(2)-GPI at different antibody concentration (A, B and C) and 3 samples of normal plasma. Thirty-five laboratories participated and interpreted their test results. All performed an ELISA for IgG aCL antibodies, while 17 also tested samples using IgG anti-beta(2)-GPI antibody ELISA. Sensitivity and specificity were calculated on the basis of the responses provided by each laboratory. Overall, 99/105 samples were correctly interpreted as positive and 97/101 as negative for the presence of IgG aCL, corresponding to a sensitivity and specificity of 94% and 96%, respectively. Likewise, 46/51 samples were correctly defined as positive and 50/51 as negative for the presence of IgG anti-beta(2)-GPI corresponding to a sensitivity and specificity of 90% and 98%, respectively. A wide variability in results pertaining to the positive samples was found for aCL-ELISA (coefficient of variation of 79%, 59%, and 53% for samples A, B, and C, respectively) as well as for abeta(2)-GPI-ELISA (coefficient of variation of 85%, 95%, and 50% for samples A, B, and C, respectively). This was confirmed when the analysis was restricted to those centres using the same commercial kit. Median antibody concentrations reported by centres for positive samples were consistent with the prolongation of coagulation tests assessing lupus anticoagulant (LA). Among these, dRVVT showed a good sensitivity and linear correlation with aCL antibody concentration. In conclusion, on the whole this survey found correct interpretation of positive and negative samples by both ELISAs. Nonetheless the high variability of reported data remains a major problem that only a consensus on the part of laboratories and manufacturers to utilize standard, uniform materials and procedures can hope to overcome.
We present a unique case of a woman with multiple painful dermal lesions localized to the left upper quadrant of the body. Histological investigation revealed microvascular thrombosis with capillary-wall proliferation. Further investigation revealed a very high anticardiolipin IgG titre and a left subclavian stenosis, presumably providing the reduced blood flow and relative hypoxia to allow microthromboses to occur in the presence of a thrombophilic tendency. Similar clinical and histological features have been reported in patients with the antiphospholipid syndrome and cases of reactive angioendotheliomatosis (RAE). This case represents a unique variant of RAE.