title: Phospholipid membranes form specific nonbilayer molecular arrangements that are antigenic.
abstract: Hexagonal phase (H(II))-preferring lipids such as phosphatidate, cardiolipin, and phosphatidylserine form nonbilayer molecular arrangements in lipid bilayers. While their presence in biological membranes has not been established, in vitro studies suggest that alterations in membrane properties modify their function. In this study, antiphospholipid monoclonal antibodies were developed against nonbilayer structures. One of the monoclonal antibodies identifies nonplanar surfaces in liposomes and in membranes of cultured cells. These results are the first evidence that natural membranes maintain a fragile balance between bilayer and nonbilayer lipid arrangements. Therefore, these antibodies can be used to evaluate the role of H(II)-preferring lipids in the modulation of membrane activities. Our studies demonstrated that nonplanar surfaces are highly immunogenic. Although these structures are normally transient, their formation can be stabilized by temperature variations, drugs, antibiotics, apolar peptides, and divalent cations. Our studies demonstrated that abnormal exposure of nonbilayer arrangements may induce autoimmune responses as found in the antiphospholipid syndrome.
authors.affiliation: Department of Biochemistry, National School of Biological Science, Instituto Politécnico Nacional, Apartado Postal 4-897, Admon. 4, México City 06401, México.
authors.forename: L
authors.initials: L
authors.lastname: Aguilar
authors.forename: G
authors.initials: G
authors.lastname: Ortega-Pierres
authors.forename: B
authors.initials: B
authors.lastname: Campos
authors.forename: R
authors.initials: R
authors.lastname: Fonseca
authors.forename: M
authors.initials: M
authors.lastname: Ibáñez
authors.forename: C
authors.initials: C
authors.lastname: Wong
authors.forename: N
authors.initials: N
authors.lastname: Farfán
authors.forename: J M
authors.initials: JM
authors.lastname: Naciff
authors.forename: M A
authors.initials: MA
authors.lastname: Kaetzel
authors.forename: J R
authors.initials: JR
authors.lastname: Dedman
authors.forename: I
authors.initials: I
authors.lastname: Baeza
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D000918:Antibody Specificity; D000954:Antigens, Surface / Q000737:chemistry* / Q000276:immunology*; D008081:Liposomes / Q000276:immunology*; D051379:Mice; D010743:Phospholipids / Q000737:chemistry* / Q000276:immunology*
chemical_list: D000906:Antibodies; D000954:Antigens, Surface; D008081:Liposomes; D010743:Phospholipids