John A. McIntyre

Antiphospholipid antibodies: discovery, definitions, detection and disease

Antiphospholipid antibodies (aPL) are immunoglobulins of IgG, IgM and IgA isotypes that target phospholipid (PL) and/or PL-binding plasma proteins. Detection of aPL in the laboratory is done currently by both immunoassays and functional coagulation tests. Convention defines aPL specificity in immunoassays according to the particular PL substrate present, for example aPS represents antiphosphatidylserine antibodies. This may be technically incorrect inasmuch as a particular PL may be responsible for binding and highly concentrating a specific plasma protein, the latter then becomes the target for the aPL. The binding of beta(2)GP-I (apolipoprotein H) to the negatively charged PL, cardiolipin (CL) provides a good example of this circumstance. In contrast, aPL which specifically prolong coagulation times in in vitro are called lupus anticoagulants (LA). The precise PL target(s) of the aPL responsible for LA activities are unknown and often debated. The persistent finding of aPL in patients in association with abnormal blood clotting and a myriad of neurological, obstetrical and rheumatic disorders often compounded by autoimmune diseases has led to an established clinical diagnosis termed antiphospholipid syndrome (APS). The common denominator for these APS patients is the presence of circulating aPL on two or more occasions and the observation of events attributable to abnormal or accelerated blood clotting somewhere in vivo. The purpose of this review is to collect, collate, and consolidate information concerning aPL.

Henoch–Schönlein purpura and stroke: Antiphosphatidyl-ethanolamine antibody in CSF and serum

Article abstract A 15-year-old girl with features of Henoch-Schönlein purpura and brain infarct had a transient IgA antiphosphatidylethanolamine antibody (aPE) in her serum and CSF that disappeared 5 months after presentation. Serum aPE is known to be associated with thrombotic events. The authors found no aPE in the CSF of two control individuals or in the serum of two patients with active Henoch-Schönlein purpura without neurologic involvement. The patient may represent a variant of antiphospholipid antibody syndrome.

ANTIPHOSPHOLIPID ANTIBODIES: Risk Assessments for Solid Organ, Bone Marrow, and Tissue Transplantation

The literature pertaining to transplantation of solid organs, bone marrow, and other tissues in aPL-positive patients has been reviewed. The effects that aPL have relative to BMT are altogether different than those ascribed to solid organs and tissues. By definition, the transplantation of allogeneic bone marrow serves to reconstitute the recipient with a completely new and genetically different repertoire of antibody-producing cells. Previously aPL-positive bone marrow recipients become aPL-negative subsequent to transplantation assuming that the marrow donor is aPL-negative. These observations are the basis for contemporary experimental approaches to curing certain autoimmune diseases with BMT. Similarly, it would follow that an aPL-negative patient provided cells from an aPL-positive donor could become aPL-positive and suffer increased risk for thrombosis. From the data provided in most of the non-bone marrow publications, the presence of aPL should be considered a grave risk factor for any potential solid organ or tissue transplant candidate. Peritoneal dialysis patients seem to be at maximal risk. Given the serious emotional and economic impact of irreversible thrombotic loss suffered by organ transplant recipients, these factors alone should justify the modest expense of pretransplant aPL screening. In the United States, the average cost of losing a kidney transplant to aPL-associated thrombosis was estimated from 1996 data to be

Antiphospholipid and glutamic acid decarboxylase antibodies in patients with focal epilepsy

82,000. The cost of losing a heart or liver is measured not only in dollars but often in the patients life. The encouraging news, however, is that once aPL are identified before transplantation, prophylactic anticoagulation seems to be capable of forestalling untoward aPL-associated allograft events. Clearly, much remains to be discovered in exploring the pathobiologic characteristics of aPL in the laboratory as well as in neutralizing their procoagulant effects at the bedside.

Redox-Reactive Autoantibodies: Biochemistry, Characterization, and Specificities

Autoantibodies to glutamic acid decarboxylase (GAD-A) have been associated with focal epilepsy.1 GAD catalyzes the conversion of l-glutamic acid to gamma aminobutyric acid (GABA). GABA is an inhibitory neurotransmitter and indirect suppression of GABA via GAD-A, in theory, could favor the development of seizures. Although originally implicated in the pathogenesis of type I diabetes and stiff-person syndrome,2 GAD-A have been identified in 8 of 51 (12%) patients with focal epilepsy due to conditions including hippocampal sclerosis.1 We attempted to further investigate the presence of GAD-A in a sample of patients with medically refractory focal epilepsy with mesial temporal sclerosis (MTS).nnAntiphospholipid antibodies (aPL) have been associated with thromboembolic events, although some have found these antibodies in the serum of patients with seizures unrelated to thromboembolic events.3 A lupus anticoagulant associated with late onset epilepsy was reported in four adults,3 …

Redox-Reactive Autoantibodies in Cerebrospinal Fluids

Oxidation–reduction (redox) reactions can “unmask” autoantibody activity in blood and other body fluids from normal, healthy individuals. These “unmasked” autoantibodies are similar if not identical to autoantibodies associated with autoimmune diseases. The agents responsible for this unmasking are physiological oxidants such as hemin and likely other naturally occurring molecules in the body that contain transitional metals available for participation in redox reactions. Laboratory comparisons between oxidized and non oxidized IgG fail to show differences to account for the oxidation-induced alteration of antibody specifics. The autoantibodies unmasked by redox reactivities represent a growing list of specificities, many that are responsible for modulating and/or regulating intracellular functions. In contrast, alloantibodies, such as anti-HLA antibodies, do not exhibit susceptibility to oxidation-induced autoantibody alterations, suggesting differences in the amino acids responsible for forming the complementarity determining regions of these respective antibody molecules. We have proposed that such reversible oxidative conversions of antibody reactivities represent a heretofore undiscovered, but an evolutionary-conserved, resource of innate humoral immunity destined to maintain an immunological homeostasis.

Redox-reactive autoantibodies in Alzheimer's patients' cerebrospinal fluids: Preliminary studies

Abstract:u2002 The oxidative stress associated with increased transitional metal concentrations in neurodegenerative diseases served as the impetus for our testing the status of redox‐reactive autoantibodies in the cerebrospinal fluids from autopsy‐confirmed Alzheimers patients. Here we describe a novel family of autoantibodies capable of recognizing autoantigens subsequent to in vitro oxidation‐reduction (redox) reactions in the blood and spinal fluids of all normal individuals tested. Redox autoantibodies are not detected in conventional immunoassays, thereby differentiating them from natural and hidden autoantibodies described by others. Whereas blood‐borne redox autoantibodies can be IgG, IgM, and/or IgA, in spinal fluid the antibody isotype is limited to IgG. Autoantibodies in certain patients are reversible and disappear when exposed to oxidizing agents in vitro. One mechanism proposed to modulate the autoantibody unmasking–masking reactions relies upon redox‐driven nitrosylation of an amino acid‐containing aromatic ring, which is found within the complementarity‐determining regions (CDR) of the antibodies antigen‐binding sites. The evolutionary persistence of this novel autoantibody family indicates that they are important for immunological homeostasis and suggests that they perform necessary physiological functions. The dramatic difference in the presence of such antibodies in normal versus Alzheimers disease (AD) suggests an important immune system dysfunction in AD.

Autoantibody potential of cancer therapeutic monoclonal antibodies

Oxidation of cerebrospinal fluid (CSF) causes differential unmasking of autoantibodies in control CSF vs. that obtained from postmortem CSF samples from autopsy confirmed Alzheimers disease (AD) cases. This study demonstrates that normal CSF from both living patients and from non-demented autopsy cases contains redox-reactive autoantibodies with specificities that include antiphospholipid antibodies (aPL). In contrast, CSF from autopsy confirmed AD subjects contained little or no redox-reactive aPL autoantibodies. Tests using an in vitro rat synaptosome model showed that the oxidized CSF autoantibodies from a normal individual can cause ERK1/2 phosphorylation at a level consistent with reports of pathogenic changes found in brain tissues from AD patients. The decrease or absence of redox-reactive antibodies in CSF from Alzheimers patients suggests that these antibodies may have been previously unmasked by the oxidative conditions that exist in the CNS in AD patients. These unmasked autoantibodies could then bind to neuronal tissues and possibly participate in the initial cascade leading to the dementia in Alzheimers. To our knowledge, this is the first description of resident autoantibodies with the potential to cause brain cell damage documented in CSF without a breech in the blood–brain barrier. The untimely and inappropriate physiological unmasking of these redox-reactive autoantibodies in AD patients CSF may represent a valuable biomarker for diagnosis and progression of this and perhaps other neurodegenerative diseases which also have oxidative stress components. These novel autoantibody observations may stimulate thoughts about additional therapeutic approaches and warrant similar studies for other neurodegenerative diseases.

Anti-Phospholipid Antibodies in Cerebrospinal Fluid But Not Serum From a Boy With Psychosis

We and others have reported that multiple autoantibodies are unmasked in human polyclonal antibody preparations after exposure to physiological oxidizing agents (hemin) or electromotive force. We now have asked if oxidation unmasks autoantibody reactivities in monoclonal antibodies (mAb). To do this, we have studied 9 FDA approved mAb used therapeutically, including 4 chimeric, 4 humanized and 1 chemically modified chimeric Fab that were exposed to the physiological oxidizing agent hemin at 36°C for 20 hr. These mAb were studied for autoantibody activity to phospholipids and DNA before and after oxidation with hemin and found to develop autoantibody activities after oxidation, while retaining their original specificity as measured by mAb anti‐glycophorin A binding of erythrocytes, CD 19 binding to B lymphocytes and anti‐HLA‐A29 binding to A29‐positive lymphocytes. The finding that certain mAb have the potential to unmask autoantibody activities as a consequence of exposure to physiological redox reactions in vitro gives pause to our present understanding of the immunological basis of tolerance and concern for potential autoimmune side effects in patients receiving mAb for diagnosis or treatment.

REDOX-REACTIVE AUTOANTIBODIES

A 12-year-old African American boy with mental retardation and Aspergers disorder presented with acute psychosis. Antiphospholipid antibody testing with enzyme-linked immunosorbent assay showed increased levels of immunoglobulin G anticardiolipin antibodies in the cerebrospinal fluid, but not in the serum. Although antiphospholipid antibodies have been reported in the serum of patients with thrombotic and neurologic disorders, there are only a few reports of these antibodies in cerebrospinal fluid. This finding is consistent with a recent report of antiphospholipid antibodies found in the cerebrospinal fluid of adults with acute psychosis.