Portal capillary C4d deposits and increased infiltration by macrophages indicate humorally mediated mechanisms in acute cellular liver allograft rejection

Almost no data exist concerning the role of antibody-mediated mechanisms in human acute cellular liver allograft rejection (ACR). Therefore, the aim of this study was to determine whether ACR is associated with depositions of complement split products and increased infiltration by B-lymphocytes, plasma cells and macrophages. A total of 35 liver biopsy specimens ( ACR n=22, controls n=13) were analyzed by immunohistochemical single and double staining. The average numbers of CD20(+), CD38(+) and CD68(+) cells per portal tract were established while the presence of C4d and C3d deposits was evaluated semiquantitatively. Significantly greater numbers of CD20(+) (P = 0.029) and CD38(+) ( P = 0.014) cells were found in the ACR specimens than in the control specimens. Additionally, 50% of patients diagnosed with ACR showed C4d deposits along portal capillaries, which was associated with a significantly increased portal infiltration by macrophages (P = 0.007). Taken together these results support the involvement of humorally mediated mechanisms in some cases of ACR.