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

Cold preservation has previously been shown to decrease the antigenicity of nerve allografts, while Schwann cells remain viable. The expression of intercellular 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, was 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 preserved at 5 degrees C for 2 and 7 weeks, respectively, before processing. Immunostains using specific monoclonal antibodies and alkaline phosphatase development were performed on each sample. The relative level of expression of these 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 and 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 cold-preserved nerve allografts appears to be linked to a down-regulation of ICAM-1 and MHC class II expression.