IN-SITU HYBRIDIZATION ANALYSIS OF ICAM-1 (CD54) MESSENGER-RNA ON CONJUNCTIVAL EPITHELIUM DURING ALLERGIC INFLAMMATION

Background The intercellular adhesion molecule ICAM-1 has been detecte d by immunohistochemical methods on epithelial cells of the conjunctiv a and nose during allergic inflammation. Objective The aim of the pres ent study was to evaluate whether ICAM-1 expression on conjunctival ep ithelium derives from endogenous synthesis or is merely due to passive uptake of soluble ICAM-1 released from inflammatory cells. Methods In situ hybridization was performed using a 3' end dygoxygenin-labelled specific DNA oligonucleotide probe on fixed conjunctival smears from a llergic subjects challenged with, or naturally exposed to the allergen , and from healthy subjects. Immunocytochemistry for ICAM-1 was perfor med by alkaline phosphatase antialkaline phosphatase. Results In aller gic patients, both naturally exposed to the allergen and after specifi c challenge, a clear hybridization pattern on epithelial cells was app arent. Out of allergen exposure, some symptomfree pollinosic subjects, as well as a few healthy volunteers showed mild ICAM-1 mRNA cytoplasm ic staining in the absence of immunohistochemically detectable ICAM-1. This finding may explain the very early appearance of ICAM-1 on conju nctival epithelium following specific challenge in allergic individual s. Conclusions These results indicate that the presence of ICAM-1 on c onjunctival epithelium during allergic inflammation derives from endog enous synthesis and not from uptake of soluble ICAM-1.