Efficacy of Rituximab in Acute Cellular Rejection in Renal Transplant Patients

Inclusion criteria: 1. male or female patients age ≥ 18 at the time of the inclusion in the study 2. male or female patients after kidney transplantation if medically justifiable (cave: previous immunosuppression, particularly prior induction therapies or biologicals). 3. Proof of an acute rejection in kidney transplant according to Banff-criteria: T-cell-mediated rejection as borderline, grade IA/B, IIA/B (no v-only), if one or more results are available as significant B-cell infiltrates CD20≥20 / high power field, glomerulitis, peritubular capillaritis or C4d positivity (with the exception of ABO-incompatible transplantations) as well as patients who have no T-cell-mediated acute rejection, but signs of acute humoral rejection (as listed above according to the criteria glomerulitis, peritubular capillaritis, C4d positivity) who have to be treated according to medical opinion of the physician with steroid therapy. The evidence of rejection can be performed by a protocol or indication biopsy. 4. SV40-negativity in the biopsy 5. GFR calculated using the MDRD-Formula \> 25 ml/min/1,73 m² in the time period before the noticed rejection. 6. Presence of a negative pregnancy test and consent to a highly effective contraceptive method (i.e. failure rate less than 1% per year, which are implants, injectable contraceptives, combined oral contraceptives, intrauterine devices (only hormone spirals), sexual abstinence or vasectomy of the partner) in patients of child-bearing age. This is not required when bilateral sterilization or ovariectomy of the patient and in patients that have exclusively female sex partners. Presence of consent to a highly effective contraceptive method for male patient. 7. Informed consent Exclusion criteria: 1. Known contraindications, resp. incompatibility for Rituximab and/or for the concomitant medication 2. Administration of Rituximab within the last 12 months before inclusion 3. Simultaneous participation in an other clinical study or participation in an other clinical study within the last 30 days 4. Breastfeeding women or pregnant women 5. Persons who fail to assess essence, meaning and significance of the clinical study and act along these lines (according to § 40 Abs. 4 and § 41 Abs. 2 and Abs. 3 AMG) 6. Existence of an active CMV-infection, existence of a HIV-infection, existence of a replicative hepatitis B or C, existence of other grave infections 7. Cardiac insufficiency in phase NYHA III-IV 8. High grade cardiac arrhythmias 9. Unstable coronary heart disease 10. Poorly adjusted diabetes mellitus (HbA1c \> 10 %) at the time of the inclusion in the study. 11. State after splenectomy 12. Contra-indication referring to a renewed transplant biopsy (e.g. coagulopathy, anticoagulation) 13. Other exclusion criteria according to the estimate of the attending doctor (e.g. aggravation of the general health condition, occurrence of a malignant disease)