title: Evidence Suggesting Complement Activation and Haemolysis at Core Temperature in Patients with Cold Autoimmune Haemolytic Anaemia.
abstract: BACKGROUND
  It is unclear why haemolysis may somewhat persist in patients with cold autoimmune haemolytic anaemia (cAIHA) at 37 °C (core temperature).
  
  
  METHODS
  Seven patients with cAIHA were included in this study. Serological testing was performed using standard techniques. Bound autoantibodies (aab) on patients' RBCs were analysed by the direct antiglobulin test (DAT), dual antiglobulin test (DDAT) and flow cytometry (FC) using pre-warmed RBCs (37 °C). Temperature-dependent complement binding was determined by incubation of patients' serum samples with group O RBCs and fresh serum complement.
  
  
  RESULTS
  The DAT was strongly positive with anti-C3d in all cases, independent of season and outside temperature. Haemolysis usually improved during warm periods of time, but decompensated following febrile infections, and persisted throughout the year, though exposure to the cold was strictly avoided. In addition, trace amounts of IgM aab were infrequently detectable on patients' RBCs even at 37 °C, and complement activation was demonstrated following incubation of RBCs with the causative aab at 37 °C.
  
  
  CONCLUSIONS
  Binding of trace amounts of IgM aab at 37 °C may provide an explanation for the durable C3d-positive DAT and haemolysis in patients with cAIHA.
authors.affiliation: Institute for Transfusion Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Thilo
authors.initials: T
authors.lastname: Bartolmäs
authors.affiliation: Institute for Transfusion Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Salih
authors.initials: S
authors.lastname: Yürek
authors.affiliation: Institute for Transfusion Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Abdelwahab Hassan Ahmed
authors.initials: AH
authors.lastname: Balola
authors.affiliation: Institute for Transfusion Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Mayer
authors.affiliation: Institute for Transfusion Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Abdulgabar
authors.initials: A
authors.lastname: Salama
keywords: AIHA; Cold agglutinins; IgM; Immune haemolysis