Renal biopsies (n = 45) from patients with various forms of
glomerulonephritis (GN), comprising mesangial
IgA-GN (n = 25), focal glomerular
sclerosis (n = 13) and acute GN (n = 7), were examined by double staining immunocytochemistry (APAAP,
streptavidin-
peroxidase) using unconjugated
monoclonal antibodies (Ab) against--(i) the
CD1b antigen expressed on dendritic cells (DCs), (ii) the
invariant chain (Ii), and (iii)
biotin-conjugated Ab against
HLA-DR. In normal control kidneys (n = 7) without interstitial
inflammation, CD1b-positive DCs were not detected. Glomerular endothelial cells and a few cells in mesangial areas showed double staining with the Ab against
HLA-DR in Ii. In GN without active interstitial
inflammation (n = 9), CD1b-positive DCs were not found. In biopsies with interstitial
inflammation (n = 36) CD1b-positive DCs were found interspersed among other inflammatory cells. In seven of the biopsies showing
IgA-GN DCs were seen in the vicinity of those glomeruli that exhibited either crescents or glomerular
sclerosis with splitting of Bowman's capsule. In proximal tubular epithelial cells de novo expression of
HLA-DR/Ii-chain was only seen when DCs were present. We conclude that in different forms of GN: (i) CD1b-positive DCs play an important role in the development of interstitial
inflammation, and (ii) their presence may be related to the de novo coexpression of
HLA-DR/Ii in tubular epithelial cells, possibly mediated through the production of
interferon gamma and other
cytokines.