Immunohistochemical study of vascular lesions in severe hypertension induced by DOCA and salt administration to spontaneously hypertensive rats. In order to evaluate whether immunoglobulin deposition in vessels plays some role in the development of vascular lesions in severe hypertension, an immunohistochemical study was performed in spontaneously hypertensive rats (SHRs), to which deoxycorticosterone acetate (DOCA) and salt were administered. DOCA and salt rapidly induced severe hypertensive vascular lesions, including necrotizing arteriolitis and productive endarteritis. In these rats, considerable deposits of IgG and IgM were found in the small arteries and arterioles of the kidneys. These deposits were accompanied by complement (C3), and could be eluted by acid incubation. They were localized in periodic acid-Schiff-positive insudative lesions, which were thought to be an early phase of the hypertensive vascular lesions. These results suggest that the immunoglobulins might be bound to an unknown antigen in the vascular lesions and that some immunological mechanism mediated by the immunoglobulins is involved in the development of vascular lesions in severe hypertension. 