H. Elgabalawy et al., EXPRESSION OF ICAM-R (ICAM-3), A NOVEL COUNTER-RECEPTOR FOR LFA-1, INRHEUMATOID AND NONRHEUMATOID SYNOVIUM - COMPARISON WITH OTHER ADHESION MOLECULES, Arthritis and rheumatism, 37(6), 1994, pp. 846-854
Objective. To study the distribution of intercellular adhesion molecul
e receptor (ICAM-R, or ICAM-3), a novel ligand for the leukointegrin l
ymphocyte function-associated antigen 1 (LFA-1), in normal and rheumat
oid synovial membranes and to compare this with the distribution of IC
AM-1, ICAM-2, vascular cell adhesion molecule 1 (VCAM-1), and endothel
ial leukocyte adhesion molecule 1 (ELAM-1). Methods. We performed immu
nohistochemical analyses of frozen sections of normal and rheumatoid s
ynovial tissue using monoclonal antibodies to the molecules examined.
Results. ICAM-1 staining was detectable on the vascular endothelium an
d the synovial lining cells of both normal and rheumatoid synovial mem
branes. A variable proportion of lymphocytes infiltrating rheumatoid t
issues expressed ICAM-1. ICAM-2 staining was demonstrable in the vascu
lar endothelium of both normal and inflamed tissues, the latter demons
trating a significantly higher proportion of positive vessels. ELAM-1
staining was not detectable in normal synovial membranes but was seen
on the endothelium of a limited number of rheumatoid synovial vessels,
usually close to the synovial lining cell layer. VCAM-1 staining was
intense in both normal and rheumatoid synovial lining cells, but vascu
lar staining was weak in both. In contrast, ICAM-R staining was not de
tected in association with any synovial blood vessels, but was widely
expressed by lymphocytes and macrophages. Cells of the lining layer di
d not stain for ICAM-R. Conclusion. Although ICAM-R is a ligand for LF
A-1 and shares considerable sequence homology with ICAM-1 and ICAM-2,
it does not appear to be expressed by the endothelium of normal or inf
lamed synovial vessels. Intense expression of ICAM-R by rheumatoid syn
ovial lymphocytes and macrophages suggests that it may play a role in
processes requiring cell-cell contact, such as antigen presentation an
d homotypic aggregation.