In experimental animals, the presence of brain-derived constituents in cervical lymph nodes has been associated with the activation of local lymphocytes poised to minimize the inflammatory response after acute brain injury. In this study, we assessed whether this immune crosstalk also existed in stroke patients. We studied the clinical course, neuroimaging, and immunoreactivity to neuronal derived Ags (microtubule-associated protein-2 and N-methyl d-aspartate receptor subunit NR-2A), and myelin-derived Ags (myelin basic protein and myelin oligodendrocyte glycoprotein) in palatine tonsils and cervical lymph nodes of 28 acute stroke patients and 17 individuals free of neurologic disease. Stroke patients showed greater immunoreactivity to all brain Ags assessed compared with controls, predominantly in T cell zones. Most brain immunoreactive cells were CD68(+) macrophages expressing MHC class II receptors. Increased reactivity to neuronal-derived Ags was correlated with smaller infarctions and better long-term outcome, whereas greater reactivity to myelin basic protein was correlated with stroke severity on admission, larger infarctions, and worse outcome at follow-up. Patients also had more CD69(+) T cells than controls, indicative of T cell activation. Overall, the study showed in patients with acute stroke the presence of myelin and neuronal Ags associated with lymph node macrophages located near activated T cells. Whether the outcome of acute stroke is influenced by Ag-specific activation of immune responses mediated by CD69 lymphocytes deserves further investigation.