THE ROLE OF ADHESION MOLECULES IN THE RECRUITMENT OF HEPATIC NATURAL-KILLER-CELLS (PIT CELLS) IN RAT-LIVER

Previous studies showed that blood large granular lymphocytes (LGL), w hich possess natural killer (NK) activity, develop within rat liver si nusoids into high-density (HD) and subsequently into low-density (LD) pit cells which show an increasing level and spectrum of tumor cytotox icity. In this study, we investigated the role of adhesion molecules, such as CD2, CD11a, CD18, and CD54 in the recruitment of pit cells to the liver. Immunostaining for electron microscopy, and two color flow cytometry showed that most pit cells expressed CD2, CD11a, CD18, and C D54. After intravenous injections into rats with anti-CDS, anti-CD11a, and anti-CD18 antibodies, the number of pit cells per square millimet er in frozen sections of liver tissue decreased. Treatment of rats wit h zymosan increased the number of pit cells fivefold, whereas subseque nt treatment with anti-adhesion-molecule antibodies resulted in approx imately 60% lower number of pit cells. Anti-CD54 supposed to block CD5 4 expression on sinusoidal endothelial cells, also decreased the numbe r of pit cells. The number of blood LGL was, however, not affected by these antibodies. These results indicate that blocking of CD2, CD11a, CD18, and CD54 antigens on blood LGL and/or liver endothelium decrease d the number of pit cells in the liver. These adhesion molecules there fore play an important role in the recruitment of pit cells in the liv er.