Inclusion Criteria:  Inclusion Criteria :  Age 18-75 (women must be either postmenopausal defined as being amenorrhoeic for greater than 2 years with an appropriate clinical profile, e.g. age appropriate (>55 years old), history of vasomotor symptoms) or having documented hysterectomy and/or bilateral oophorectomy) ; Clinical evidence at presentation of anterior ST-elevation myocardial infarction (STEMI) defined as symptoms suggestive of acute myocardial ischemia, an electrocardiogram showing ST-segment elevation ≥2 mm in ≥2 contiguous leads in V1 to V4; Complete occlusion (i.e. TIMI flow 0-1) of proximal or mid left anterior descending (LAD) coronary artery on urgent angiography interpreted as the infarct-related artery (IRA); Onset of worse symptoms within 6 hours before admission; Plan to provide primary percutaneous angioplasty (PPCI) for the patient within 2 hours of ECG diagnosis; Ability to start infusion of rituximab within 3 hours of PPCI ; Written informed consent.  Exclusion Criteria:  History of previous MI; Presentation with cardiac arrest; Cardiogenic shock (defined as systolic blood pressure <90 mmHg for >30minutes, or necessitating vasopressors to achieve a blood pressure ≥90 mmHg); Cardiac electrical instability (defined as complete heart block needing temporary pacing or any tachyarrhythmia needing cardioversion); Patients with Killip class III heart failure; History of severe chronic renal failure (define as stage 4 (GFR = 15-29 mL/min) or worse); History of hepatitis B, HIV or tuberculosis; Patient positive for point of care bedside test of Ag HBs; Severe, progressive infections documented; Active COVID-19 infection or COVID-19 infection within 3 months; Patient with documented severe immune deficiency; Presence, or history in ≤ five years, of an ongoing cancer, (except in situ cancer of the cervix or basal cell carcinoma); QTcF> 450 msecs in males, > 470msecs in females; Any oral or intravenous immunosuppressive treatment, immune modulatory monoclonal antibodies or immunodepleting therapy at any time (inhalers and topical creams with corticosteroids are permitted); Previous history of major organ transplant including renal transplant; Known hypersensitivity to the active substance of MabThera® (rituximab) or to proteins of murine origin, or to any of the other excipients; Any contraindications to any of the Mabthera® premedication drugs; Contraindications to injectable Polaramine :  Risk of closed-angle glaucoma, Risk of urinary retention linked to urethro-prostatic disorders;  Expected need for vaccination with a live attenuated vaccine during the study, including incomplete vaccination courses (in case, life, attenuated vaccine must be administered at least 30 days before inclusion in study); Absence of COVID-19 vaccination (with 2 doses of COVID-19 vaccination or patient infected with COVID-19 and whom received one dose of COVID-19 vaccination);  Any obvious contraindications for MRI or conditions which will impede image acquisition for example:  Severe claustrophobia Non-MRI compatible permanent pacemaker Patients who have a metallic foreign body (metal silver) in their eye, or who have an aneurysm clip in their brain Patients who have had metallic devices placed in their back Known hypersensitivity to imaging products (gadoteric acid, meglumin or any drug containing gadolinium) Known hepatic failure; Previous history of progressive multifocal leukoencephalopathy; Inclusion in other interventional drug study within the previous 3 months; Inability to comply with study procedures; Patients under guardianship or curatorship.