Inclusion Criteria:
* Male or non-pregnant women with acute stroke symptoms aged over 18 years.
* Patients having an ischemic stroke or a TIA prior to randomization (Patients having an acute ischemic stroke within 72 hours with NIHSS score≤5 at baseline, or patients having a TIA within 72 hours with Oxfordshire Community Stroke Project on the basis of age, blood pressure, clinical features, and duration of TIA symptoms (ABCD2) score≥4 at baseline).
* The entry event is attributed to symptomatic atherosclerosis (50-99%) in an intracranial qualifying artery (intracranial carotid artery (C4-7), middle cerebral artery (M1), intracranial vertebral artery or basilar artery) confirmed by CT, MR angiography, or digital subtraction angiography.
* Informed consent obtained from patients or their legal representatives.
* Willing to be followed up as required by the clinical study protocol.
Exclusion Criteria:
* Thrombolytic therapy or thrombectomy within 24 hours prior to enrollment.
* Pre-stroke mRS score ≥ 2.
* Combined or previous intracranial hemorrhage: hemorrhagic stroke, epidural hematoma, subdural hematoma, intraventricular hemorrhage, subarachnoid hemorrhage, etc.
* Any of the following unequivocal cardiac source of embolism: chronic or paroxysmal atrial fibrillation, sinus node dysfunction, mitral stenosis, prosthetic heart valves, endocarditis, left ventricular mural thrombus or valvular vegetation, myocardial infarction within three months, dilated cardiomyopathy, spontaneous echogenic defects in the left atrium or an ejection fraction of less than 30%.
* Intracranial arterial stenosis due to arterial dissection, Moya Moya disease; herpes zoster, varicella zoster or other viral vasculopathy; neurosyphilis; radiation induced vasculopathy; fibromuscular dysplasia; sickle cell disease; neurofibromatosis; post-partum angiopathy; suspected vasospastic process, suspected recanalized embolus; any known vasculitic disease.
* Extracranial stenosis ≥50%, subclavian arterial stenosis≥50% or subclavian steal syndrome.
* Previous interventions for intracranial arterial stenosis.
* Concurrent intracranial tumors, intracranial aneurysms or arteriovenous malformations
* Neutrophil \< 2×10 9/L.
* Platelet \< 100×10 9/L.
* Serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels greater than 1.5 times the upper limit of normal.
* Active infections including localized.
* Evidence of HIV or hepatitis B positivity.
* Positive tuberculosis-related tests.
* Concurrent peptic ulcer, diverticulitis or inflammatory bowel disease.
* Concurrent malignant tumors, recent bone marrow transplant or recent organ transplant.
* Systolic blood pressure ≥ 180 mmHg or diastolic blood pressure ≥ 110 mmHg despite blood pressure control.
* Known allergy to tocilizumab or excipients.
* Use of immunosuppressive drugs or systemic use of antibiotics.
* Received any live or live attenuated vaccine within 4 weeks prior to enrollment or plan to receive a live or live attenuated vaccine during the study.
* History of demyelination or presence of neurological symptoms suggestive of demyelination.
* Previously existing neurological or psychiatric disorders that could potentially confuse neurological function assessment.
* An expected survival less than 90 days.
* Participation in another interventional clinical study.
* Patients unsuitable for enrollment in the clinical trial according to investigators decision making.
