MONOCYTE/MACROPHAGES AND C4d IN RENAL ALLOGRAFTS Alex Magil, MD

BACKGROUND ACUTE HUMORAL REJECTION (AHR) C´ split factor C4d generated by Ag-Ab reaction C4d binds covalently to PTC endothelium & BM PTC C4d is a putative marker for AHR Associated with poor outcome

BACKGROUND Cont’d MONOCYTE/MACROPHAGE (MO) Component of the inflammatory infiltrate in acute rejection Prominent numbers associated with poor outcome C´ split factor C5a is chemotactic for MO Uncertain whether MO has a role in AHR

Hypothesis There is a significant association between PTC C4d deposition and MO infiltration in acute allograft rejection

Study Design Compare glomerular & interstitial MO & PMN infiltration in C4d + and C4d – biopsies All biopsies showing strong diffuse PTC C4d staining done between Jan. 1, 1999 and June 30, 2002 – C4d+ Group All biopsies showing ACR negative for C4d done between Jan. 1, 1999 and Dec. 31, 1999 – C4d- Group For each biopsy - mean no. MO/glomerulus - mean no. PMN/glomerulus - mean no. CI MO/hpf - mean no. PTC PMN/hpf All biopsies graded according to Banff 97 criteria

Peritubular Capillary C4d

Acute Cellular Rejection

Suspicious for AHR (C4d +)

Glomerulitis

Glomerular CD 68+ Cells

Interstitial CD 68+ Cells

Pathological Criteria for AHR C4d deposition in peritubular capillaries (PTC) At least one of the following: ≥2.0 PTC neutrophils per hpf arterial fibrinoid necrosis acute tubular injury Circulating donor-specific antibodies Mauiyeddi et al: JASN 13: , 2002

Results – Banff 97 Grade Suspicious1A1B2A3 C4d C4d

Patient Characteristics C4d+C4d-P No. of Patients1524 Male:Female5:1019: % with 2 nd or 3 rd TX % with PRA > 20%

General Histological Results C4d+C4d-P No. of Biopsies2328 % with Glomerulitis % with ≥ 1.0 PMN/GLOM % with ≥ 2.0 PTC PMN/hpf90NS % with Neutrophilic Tubulitis

Glomerular and Interstitial Monocytes P < P =

Glomerular and PTC Neutrophils P = P =

Glomerular MO and Outcome P= MO/GLOM≥0.5MO/GLOM<0.5

Association of Glomerular MO and C4d with Outcome MO<0.5MO≥0.5MO<0.5MO≥0.5 P=

Conclusions There is a strong association of glomerular and interstitial MO infiltration with PTC C4d The sensitivity (91%) and specificity (93%) of glomerular MO infiltration (mean MO/GLOM ≥ 1.0) for the C4d group suggest that glomerular MO be added to the current criteria for AHR

Acknowledgments Kathryn Tinckam Ognjenka Djurdjev David Landsberg Paul Keown