title: Re-examination of renal allograft biopsy blocks for C4d positivity: missed cases of antibody mediated rejection.
abstract: BACKGROUND
  C4d immunostaining of renal allograft biopsies is recommended for the diagnosis of antibody-mediated rejection (ABMR), but it was not available to us prior to June 2012. In June 2012, we were able to obtain anti-human C4d polyclonal antibody and decided to retrospectively evaluate archived kidney allograft biopsies at our center for C4d deposition.
  
  
  METHODS
  Twenty-four paraffin blocks were available for this study. Immunostaining for C4d was performed using anti-human C4d polyclonal antibody by Immunohistochemistry. The score and pattern of C4d positivity were determined according to the Banff 2007 guidelines.
  
  
  RESULTS
  All grafts were from living related donors with negative CDC cross-match. The indications for biopsy were primary, acute and chronic graft dysfunction in 29.2%, 33.3% and 37.5% of patients respectively. Two biopsies revealed extensive necrosis rendering it difficult to interpret the result of C4d staining. Among the remaining 22 biopsies, C4d staining was categorized as negative in 40.9%, minimal in 13.6%, focal in 22.7% and diffuse in 22.7%. The prevalence of C4d positivity among biopsies taken due to primary, chronic and acute graft dysfunction was 71.4%, 44.4% and 12.5% respectively.
  
  
  CONCLUSIONS
  C4d positivity was common in biopsies taken from this group of kidney transplant recipients and its prevalence was particularly high among biopsies taken due to primary graft non-function. This indicates that missed ABMR is an important cause for kidney allograft dysfunction in our setting.
authors.affiliation: Faculty of medical laboratory sciences, Khartoum University, Khartoum, Sudan.
authors.forename: Hiba E
authors.initials: HE
authors.lastname: Mohamed
authors.affiliation: Faculty of medical laboratory sciences, Khartoum University, Khartoum, Sudan.
authors.forename: Israa I
authors.initials: II
authors.lastname: Hammad
authors.affiliation: Ahmed Gasim Cardiac Surgery and Kidney Transplant Center,Khartoum, Sudan.
authors.forename: Sarra
authors.initials: S
authors.lastname: Elamin
authors.affiliation: Faculty of Medical Lab Sciences, Alzaeim Alazhari University, Khartoum, Sudan.
authors.forename: Elwaleed M
authors.initials: EM
authors.lastname: Elamin
authors.affiliation: Faculty of medical laboratory sciences, Khartoum University, Khartoum, Sudan.
authors.forename: Anaheed I
authors.initials: AI
authors.lastname: Ibrahim
authors.affiliation: Ahmed Gasim Cardiac Surgery and Kidney Transplant Center,Khartoum, Sudan.
authors.forename: Abdul-Rahman A
authors.initials: AR
authors.lastname: El-Magzoub
authors.affiliation: Ahmed Gasim Cardiac Surgery and Kidney Transplant Center,Khartoum, Sudan.
authors.forename: Ishraqa A
authors.initials: IA
authors.lastname: Farragallah
authors.affiliation: Faculty of Medicine, Ahfad University for Women, Khartoum, Sudan.
authors.forename: Lamyaa A M
authors.initials: LA
authors.lastname: Elhasan
authors.affiliation: Institute of Endemic diseases, Khartoum University, Khartoum, Sudan.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Elhasan
mesh_terms: D000293:Adolescent; D000328:Adult; D064591:Allografts; D002648:Child; D015935:Complement C4b / Q000378:metabolism*; D005260:Female; D006084:Graft Rejection / Q000276:immunology; D006801:Humans; D007150:Immunohistochemistry; D016030:Kidney Transplantation / Q000009:adverse effects* / Q000379:methods; D019520:Living Donors; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D015935:Complement C4b