Tissue injury, craniotomy, and anaesthesia result in rapid alteration of leukocyte responses. Extracranial tissue injury results in increased proportion (A) and cell numbers (B) of granulocytes in the circulation, which is indistinguishable from changes induced by sham surgery or MCAo. Blood samples taken from the tail vein prior to surgery and 60 min after the onset of MCAo/control surgery (0 min reperfusion) are shown. (C) Representative dot plots showing terminal cardiac blood samples at 4 h reperfusion for graphs (D–G). P3 gate: Ly6G+ granulocytes, P4 gate: MHCII+ B cells (dark blue color indicates CD19+ positive cells). Proportion (D) and total cell numbers (E) of granulocytes in cardiac blood samples at 4 and 72 h reperfusion. Proportion (F) and total cell numbers (G) of MHCII+ B cells (CD19+) in cardiac blood samples at 4 and 72 h reperfusion. Sham no cran.—sham surgery without craniotomy. n = 5, 4, 4, 5, 6–7, 3, 3 in naïve, isoflurane, sham no cran., sham, MCAo, sham 72 h, and MCAo 72 h, respectively. *P < 0.05, **P < 0.01, ***P < 0.001 vs. naive. Light blue color indicates negative (unstained) population.