Graft failure remains a major problem after renal transplantation. Identification of acute humoral rejection in biopsy specimens has been problematic because no morphologic feature described to date is either pathognomonic or universal. In the present study, we investigated the role of both c4d and fibrin as diagnostic tools for early assessment of acute humoral rejection.
Patients and Methods:

This work represents a retrospective study on 53 renal allograft biopsies at the period between January 2005 till May 2008 in Urology and Nephrology center (Mansoura Faculty of Medicine). Alternate slides were stained with hematoxylin and eosin stains (H&E), periodic acid- Schiff stain (PAS) and Masson trichrome stain (MT), as routine workup following standard procedures for staining. Cases of acute humoral rejection were previously stained for C4d by immunohistochemical technique. For the immunofluorescent staining, the pretreated sections are stained by monoclonal C4d and fibrinogen antibodies using indirect immunofluorescent method.
Results& Conclusion:

-Statistically significant higher C4d positivity by immunofluorescence staining in cases of acute humoral rejection was found in comparison to C4d immunohistochemical staining (p<0.01).
- The fibrin positivity in cases of acute humoral rejection was higher than cases of acute cellular rejection, that was statistically significant (p<0.05).
- non significant relation between consanguinity and recepient patients (pvalue>0.05).
- This study concluded that C4d has a role in detection and diagnosis of acute humoral rejection cases and this can modify the protocol of treatment for better graft survival. Fibrin detection is important for diagnosis of missed cases of fibrinoid necrosis which are specific for acute humoral rejection cases and were not confirmed by routine light microscopic staining.