A comparative immunohistological study was performed for the glomerular deposition of complements (C1q and C3c), fibrin/fibrinogen-related antigen (FRA), the expression of ICAM-1 and the infiltration of leukocytes bearing β2 integrins (LFA-1, CR3 and CR4) on renal biopsy specimens from 49 cases with Henoch-Schoenlein purpura nephritis (HSPN) and age-matched 49 cases with IgA nephropathy (IgAN).
　　The glomerular expression of ICAM-1 was signifcantly correlated with the glomerular infiltration of LFA-1⁺ leukocytes in both diseases and with that of CR3⁺ leukocytes in HSPN. The expression of ICAM-1 was closely localized with the infiltration of LFA-1⁺ leukocytes in the study with double immuno-staining. The incidence and intensity of glomerular deposition of FRA were significantly higher in HSPN than in IgAN (P<0.001), and those of C3c were significantly lower in HSPN than in IgAN (P<0.001). The glomerular deposition of FRA was significantly correlated with the glomerular infiltration of CR4⁺ leukocytes in HSPN (P<0.05) but not in IgAN. In contrast, the glomerular deposition of C3c was significantly correlated with the glomerular infiltration of CR4⁺ leukocytes in IgAN (P<0.05) but not in HSPN. Studies with double immuno-staining revealed close association of CR4⁺ leukocytes with FRA deposition in HSPN and with C3c deposition in IgAN respectively. The number of glomerular leukocytes bearing β2-integrins was significantly correlated with urinary protein at the time of renal biopsy in both diseases.
　　These results suggested the differential roles of β2 integrins in the induction of glomerular injury in HSPN and IgAN. The ICAM-1/LFA-1 interaction may commonly be involved in the glomerular infiltration of leukocytes in both diseases. ICAM-1/CR3 interaction may be involved only in HSPN. CR4 may function as a fibrin/fibrinogen receptor in HSPN while CR4 may function as a complement receptor in IgAN.