The primary objective of the study is to compare the immunological status after either autologous blood transfusion as administered by Bellovac® ABT or allogenic blood transfusion, with regards to change in Natural Killer (NK) cell frequency in patients undergoing total knee replacement.

Inclusion Criteria:

• Provision of informed consent
• Male and female patients aged 18 years and over scheduled for total knee replacement
• Subjects classified as ASA Physical Status Classification System class P1, P2 or P3 according to the American Society of Anaesthesiology

Exclusion Criteria:

• Involvement in the planning and conduct of the study (applies to both Astra Tech staff or staff at the study site)
• Pre-operatively haemoglobin below normal range as judged by the investigator
• Previous enrolment or randomisation to treatment in the present study
• Expected or confirmed participation in another clinical study during the study period
• Severe non-compliance to protocol as judged by the investigator and/or Astra Tech
• Current symptoms of haemophilia
• History of or presence of malignant disease with propensity for systemic spread during the last 5 years
• Current or expected use of cytotoxic drugs
• Current untreated anaemia (e.g. sickle cell anaemia) as deemed by investigator
• Use of pre-donation
• Use of recombinant erythropoetin
• Use of other autologous blood transfusion than that with Bellovac ABT, e.g. washed and centrifuged blood like CellSaver