-One third of cases of cerebral ischemia have no clear etiology. A humoral response to the atherosclerotic plaques components beta2-glycoprotein I (beta2-gpI) and heat-shock proteins (Hsp) might be involved in the pathogenesis of stroke. This case-control study includes a complete profile of anti-beta2-gpI antibodies and testing of IgG antibodies to the 60/65 kilodaltons (kDa) Hsp in stroke patients. Ninety-three patients with acute ischemic stroke and 93 controls were evaluated for age, sex, race, hypertension, smoking, previous cardiopathy, diabetes mellitus, hypercholesterolemia and previous history of cerebral ischemia. IgG/ IgM/IgA anticardiolipin (aCL) and anti-beta2-gpI antibodies, as well as IgG antibodies to human 60 kDa Hsp and to Mycobacterium bovis 65 kDa Hsp, were detected by immunoassay. Adjusted odds ratios (OR) were calculated by logistic regression. The adjusted OR for IgA anti-beta2-gpI antibodies was 4.6 (90%CI 1.5 to 14.3; p = 0.025). The non-adjusted OR for IgG antibodies to Hsp 60 was 26.1. The adjusted OR for IgG antibodies to Hsp 65 was 3.2 (90%CI 1.2 to 8.3; p = 0.044). The adjusted OR for IgG to any Hsp (60 or 65) was 4.8 (90%CI 1.9 to 12.1; p = 0.006). This study demonstrates that elevated IgA anti-beta2-gpI and IgG antiHsp 60/65 antibodies are associated with increased risk of ischemic stroke. The association occurred independently of other risk factors. This humoral response might link autoimmunity, thrombophilia and atherosclerosis in stroke patients.KEY WORDS: anti-beta2-gpI antibodies, anti-Hsp 60/65 antibodies, acute cerebral ischemia.Anticorpos contra os componentes da placa aterosclerótica beta2-glicoproteína I e proteínas de choque Anticorpos contra os componentes da placa aterosclerótica beta2-glicoproteína I e proteínas de choque Anticorpos contra os componentes da placa aterosclerótica beta2-glicoproteína I e proteínas de choque Anticorpos contra os componentes da placa aterosclerótica beta2-glicoproteína I e proteínas de choque Anticorpos contra os componentes da placa aterosclerótica beta2-glicoproteína I e proteínas de choque térmico como fatores de risco para isquemia cerebral aguda térmico como fatores de risco para isquemia cerebral aguda térmico como fatores de risco para isquemia cerebral aguda térmico como fatores de risco para isquemia cerebral aguda térmico como fatores de risco para isquemia cerebral aguda RESUMO -Um terço dos casos de isquemia cerebral não apresenta etiologia clara. Uma resposta humoral contra os componentes da placa aterosclerótica beta2-glicoproteína I (beta2-gpI) e proteínas de choque térmico ("heat-shock proteins", Hsp) pode estar envolvida na patogênese do infarto cerebral. Este estudo de caso-controles inclui um perfil completo de anticorpos anti-beta2-gpI e a testagem de IgG anti-Hsp de 60/65 kilodaltons (kDa) em pacientes com isquemia cerebral. Noventa e três pacientes com isquemia cerebral aguda e 93 controles foram avaliados quanto a idade, sexo, raça, hipertensão arterial, tabagismo, cardiopatia prévia, diabete mellitus, hip...