Biomedical subjects

L R Sammaritano

Publications and source records attributed to L R Sammaritano.

25 records · Page 2Linked to original sources

PubMed1992

Phospholipid binding of antiphospholipid antibodies and placental anticoagulant protein.

We evaluated the interaction of antiphospholipid antibodies (aPL) with placental anticoagulant protein I (PAP I), a calcium-dependent phospholipid binding protein which may act as a natural anticoagulant. Clotting assays showed additive prolongation of clotting times with aPL and PAP I. ELISA and vesicle phospholipid binding studies showed PAP I inhibition of aPL binding to phospholipid but no inhibition of PAP I-phospholipid binding by aPL. aPL and PAP I interact additively in anticoagulant activity in in vitro clotting systems and compete for phospholipid in ELISA system. These data support the hypotheses that aPL and PAP I may recognize similar phospholipid epitopes and that in vivo interaction may occur.

Annexins↗

PubMed1992

Induction of antiphospholipid autoantibodies by immunization with beta 2 glycoprotein I (apolipoprotein H).

A subset of patients with systemic lupus erythematosus has autoantibodies to acidic phospholipids. Since lipids are poor immunogens, the mechanism responsible for the induction of these antibodies is unclear. Immunization of a normal rabbit and normal mice with purified human beta 2-glycoprotein I (apolipoprotein H) resulted in the production of high levels of two non-cross-reactive antibody populations, anti-apolipoprotein H, and antiphospholipid. The antiphospholipid antibodies had binding specificities indistinguishable from autoantibodies obtained from human and murine lupus. These findings suggest a novel mechanism for the induction of antiphospholipid autoantibodies.

Animals↗

PubMed1992

Antiphospholipid antibodies differ in aPL cofactor requirement.

Although autoimmune antiphospholipid antibodies (aPL) may require a serum cofactor, beta 2-glycoprotein I (beta 2GPI), for maximal binding in aPL ELISA, it is not known whether cofactor is absolutely required or is merely an enhancing factor for binding, nor is it clear whether aPL bind to cofactor itself, a cofactor-lipid complex, or a phospholipid modified in some way by cofactor. We therefore isolated and purified beta 2GPI and evaluated its relationship to both IgG and IgM aPL binding. aPL derived from different sera appear to have differing requirements for cofactor; the proportion of total binding attributable to cofactor varies from 46% to 95%. aPL do not bind to beta 2GPI in the absence of phospholipid. Enhanced binding to phospholipid is seen if beta 2GPI is provided either before or with the test antibody. Autoimmune aPL bind phospholipid better with human rather than bovine cofactor. The requirement for cofactor is greater for low-avidity aPL as measured in an IgG-human cofactor system. Cofactor requirement alone does not predict the presence or absence of associated clinical complications.

Antibodies, Antiphospholipid↗

PubMed1992

Antiphospholipid antibody syndrome.

Autoimmune aPL are associated with a well-defined clinical syndrome of vascular thromboses, recurrent fetal loss, thrombocytopenia, livedo reticularis, and valvular and neurologic abnormalities. A clinical diagnosis of SLE need not be present, and aPL syndrome in the absence of other well-defined autoimmune disease is termed PAPS. A positive test for aPL is defined by enzyme-linked immunoassay (aCL) or by functional coagulation assay (LAC). Anticardiolipin antibody and LAC are similar but probably not identical antibodies. The false-positive test for syphilis is less closely associated with clinical complications than are aCL and LAC. The mechanism of action of aPL is not yet known, although many theories have been advanced. Recent identification of beta 2-glycoprotein I, a serum glycoprotein, as an aPL cofactor suggests that inhibition of this protein's anticoagulant activity may be important. Autoimmune aPL differ from infection-induced aPL in important antibody characteristics, including IgG subclass, light chain preference, antibody avidity, and cofactor requirement. Both recognize negatively charged phospholipids, but various physical characteristics of the phospholipids alter the recognition patterns. Treatment of the aPL syndrome is not well defined. Anticoagulation with heparin, coumadin, or aspirin are currently widely used. Although corticosteroid, immunosuppressive therapy, and plasmapheresis may be used for severe, fulminant thrombosis, the efficacy of this treatment has yet to be proved.

Animals↗

PubMed1990

Fatty acid chain is a critical epitope for antiphospholipid antibody.

To explore the role of phospholipid fatty acids in binding of antiphospholipid antibody (aPL) in ELISA, we tested aPL binding to phospholipids containing fatty acids of varying chain length and degree of saturation using direct ELISA and inhibition methods. Polyclonal IgG and IgM human aPL's bind to C18:1 phosphatidylglycerol (PG) better than to C18:0 PG or C18:2 PG. Binding is greater to C18 than to C14:0 or C16:0 PGs; aPL's do not bind to C12:0 PG. aPL binding is not inhibited by C18:1 diacylglycerol, glycerol-3-phosphate, myoinositol, or myoinositol phosphate. The fatty acid chains are critical determinants for antigen recognition and, by projection, biological activity of aPL.

Autoantibodies↗

PubMed1990

Antiphospholipid antibody syndrome: immunologic and clinical aspects.

Antiphospholipid antibody is associated with a clinical syndrome of vascular thrombosis, thrombocytopenia, recurrent fetal loss, and livedo reticularis, whether or not a clinical diagnosis of systemic lupus erythematosus (SLE) coexists. A positive antiphospholipid antibody test is defined by enzyme-linked immunosorbent assay (ELISA) (antiphospholipid antibody itself) or by coagulation assay (lupus anticoagulant). These are similar but not identical antibodies. The test for syphilis is less closely related to the preceding two and is less regularly associated with clinical complications. The mechanism of action of either antiphospholipid antibody or lupus anticoagulant is as yet unknown. SLE-induced but not infection-induced antiphospholipid antibody has immunoglobulin G2 (IgG2) and IgG4 predominance. It recognizes all negatively charged phospholipids, but various physical characteristics of the phospholipids alter the recognition patterns. Treatment for the antiphospholipid antibody syndrome has not been clearly defined. Anticoagulation with aspirin, heparin, or warfarin is currently favored. A role for corticosteroid remains to be demonstrated.

Antibodies↗

PubMed1990

Characteristics of IgG antiphospholipid antibodies in patients with systemic lupus erythematosus and syphilis.

To evaluate the similarities and differences of antiphospholipid antibodies (aPL) in systemic lupus erythematosus (SLE) and syphilis, we studied 20 SLE and 16 syphilis high titer IgG aPL sera for antibody isotype, avidity, phospholipid specificity, light chain and IgG subclass. Syphilis aPL had lower avidity, with kappa light chain and IgG1 and IgG3 predominance, in contrast to higher avidity, with lambda light chain and IgG2 and IgG4 predominance in SLE aPL. Phospholipid specificities were similar. SLE and syphilis aPL both recognize phospholipid epitopes but differ in important antibody characteristics.

Autoantibodies↗