Cold preservation of nerve grafts decreases expression of ICAM-1 and classII MHC antigens

Cold preservation has previously been shown to decrease the antigenicity of nerve allografts, while Schwann cells remain viable. The expression of int ercellular adhesion molecule-1 (ICAM-1) and class II MHC antigens, both of which have been shown to play a major role in initiating graft rejection, w as studied in fresh rat nerve, and after 2 and 7 weeks of cold preservation . Ten sciatic nerves harvested from Lewis rats were cut into three segments . One segment was processed immediately, while the other ones were preserve d at 5 degrees C for 2 and 7 weeks, respectively, before processing. Immuno stains using specific monoclonal antibodies and alkaline phosphatase develo pment were performed on each sample. The relative level of expression of th ese antigens was compared using computer-assisted densitometry. Expression of ICAM-1 was significantly decreased at 7 weeks, as compared to fresh and 2-week groups, with no statistically significant difference between fresh a nd 2-week nerves. Expression of class II MHC was significantly decreased at 2 and 7 weeks, compared to fresh nerves, with no statistically significant difference between the preserved groups. The decrease in antigenicity of c old-preserved nerve allografts appears to be linked to a down-regulation of ICAM-1 and MHC class II expression.