DIFFERENTIAL EXPRESSION OF ADHESION MOLECULES DURING RAT SMALL-BOWEL ALLOGRAFT-REJECTION

The adhesion molecules intercellular adhesion molecule 1 (ICAM-1), lym phocyte function-associated antigen-1 (LFA-1) (alpha and beta chains), and very late activation antigen-4 (VLA-4) have an essential role in cell-cell interactions and the initiation of immune responses. This st udy used an indirect immunoperoxidase technique to investigate the exp ression of these molecules in the lamina propria of allografts and iso grafts after heterotopic rat small bowel transplantation. Normal untra nsplanted small bowel served as additional controls. Overall, ICAM-1 a nd LFA-1 alpha expression was significantly higher in allografts, alth ough there was variable expression of these molecules in isografted an imals. There were temporal differences in the expression of ICAM-1 and LFA-1 alpha in that increased ICAM-1 expression was more pronounced i n the early posttransplant period whereas there was a progressive incr ease in LFA-1 alpha as rejection developed. In contrast, there was no difference between allograft and isograft expression of LFA-1 beta and VLA-4. This study has demonstrated a preferential increase in adhesio n molecule expression with developing rat small bowel allograft reject ion and suggests that adhesion molecules are involved in the developme nt and progression of allograft rejection. Although the observed diffe rences in antigen expression are not as marked as those previously rep orted in other organ transplants, appropriate adhesion molecules may p resent suitable targets for immunotherapeutic protocols after small bo wel transplantation.