TITRATE (inducTIon for acuTe ulceRATivE Colitis)

Inclusion Criteria: 1. Admission with acute severe UC (defined patients with bloody diarrhoea ≥ 6/day and any signs of systemic toxicity (pulse \> 90/min, temperature \> 37.8°C, haemoglobin \< 105 g/l, erythrocyte sedimentation rate \[ESR\] \> 30 mm/h, or C-reactive protein \[CRP\] \> 30 mg/l) 2. Failure to intravenous steroid treatment as defined by the Oxford criteria (more than 8 stools/d or 3-8 stools/d and CRP≥45) and a Lichtiger score ≥ 10 on day 3 after starting iv steroid treatment 3. Patients going through baseline endoscopy and biopsy sampling (including CMV) before starting on IFX treatment 4. In the opinion of the investigator, the subject is capable of understanding and complying with protocol requirements. 5. The subject signs and dates a written, informed consent form and any required privacy authorization prior to the initiation of any study procedures. 6. Male or non-pregnant, non-lactating females. Females of child bearing potential must have a negative serum pregnancy test prior to randomization, and must use a hormonal (oral, implantable or injectable) or barrier method of birth control throughout week 26. Females unable to bear children must have documentation of such in the source records (i.e., tubal ligation, hysterectomy, or post-menopausal \[defined as a minimum of one year since the last menstrual period\]). Exclusion Criteria: 1. Patients at imminent need of surgery as judged by the treating clinician 2. Previous use of IFX 3. Enteric pathogens (such as Salmonella, Shigella, Yershinia, Campylobacter and C. difficile) detected by stool analysis within 2 weeks prior to enrollment or at screening 4. Active participation in another interventional trial 5. Patients with Crohn's disease or IBD-U 6. Patients with abdominal abscess 7. Patients with colonic stricture 8. Patients with a history of colon cancer or colonic dysplasia, unless sporadic adenoma, which has been removed 9. Active or latent tuberculosis (screening according to national guidelines) 10. Cardiac failure in NYHA stage III-IV 11. History of demyelinating disease 12. Recent live vaccination 13. Patients with ongoing acute/chronic infection (including but not limited to HIV, hepatitis B and C) with the exception of chronic herpes labialis or cervical HPV 14. History of cancer in the last 5 years with the exception of non-melanoma skin cancer 15. A history of alcohol or illicit drug use that in the opinion of the principal investigator (PI) would interfere with study procedures 16. Patients with psychiatric problems that in the opinion of the PI would interfere with study procedures 17. Patients unable to attend all study visits 18. Patients with a history of non-compliance with clinical study protocols 19. Contraindication for endoscopy 20. Patients who received any investigational drug in the past 30 days or 5 half-lives, whichever is longer 21. Patients who received cyclosporine in the previous 14 days 22. Pregnancy and lactation