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 +)

Suspicious for AHR (C4d +)

Glomerulitis

Glomerular CD 68+ Cells

Interstitial CD 68+ Cells

0

10

20

30

40

50

60

70

80

90

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

EastWestNorth

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 13:234-241, 2002

Results – Banff 97 Grade

Suspicious 1A 1B 2A 3

C4d+ 16 5 0 2 0

C4d- 0 13 4 10 1

Patient Characteristics

C4d+ C4d- P

No. of Patients 15 24

Male:Female 5:10 19:5 0.0116

% with 2nd or 3rd TX 40 8 0.0483

% with PRA > 20% 62 12 0.0038

General Histological Results

C4d+ C4d- P

No. of Biopsies 23 28

% with Glomerulitis 57 11 0.0014

% with ≥ 1.0 PMN/GLOM 22 7 0.1193

% with ≥ 2.0 PTC PMN/hpf 9 0 NS

% with Neutrophilic Tubulitis

35 11 0.0823

Glomerular and Interstitial Monocytes

0

2

4

6

8

10

12

14

MO/GLOM CI MO/hpf

C4d+

C4d-

P < 0.0001 P = 0.0030

3.40.2

12.9

6.5

Glomerular and PTC Neutrophils

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

PMN/GLOM PTC PMN/hpf

C4d+

C4d-

P = 0.0003 P = 0.0035

0.8

0.3

0.9

0.4

Glomerular MO and Outcome

0

10

20

30

40

50

60

EVENT

NO EVENT

P=0.0027

13

21

8

57

MO/GLOM≥0.5 MO/GLOM<0.5

Association of Glomerular MO and C4d with Outcome

0

10

20

30

40

50

60

C4d- C4d- C4d+ C4d+

EVENT

NO EVENT

MO<0.5 MO≥0.5 MO<0.5 MO≥0.5

P=0.0109

8

51

8 9 0 6 5

12

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