EFFECTS OF EX-VIVO MANIPULATION ON THE EXPRESSION OF CELL-ADHESION MOLECULES ON NEUTROPHILS

In vitro studies of neutrophil adhesion generally utilise purified pop ulations and are often performed at 37 degrees C. This study determine s the effects of temperature changes and neutrophil separation procedu res on the expression of cell adhesion molecules on neutrophils. We fo und that neutrophil separation procedures involving erythrocyte sedime ntation and hypotonic lysis are associated with a significant increase in the expression of both a structural and functional epitope of the beta(2) integrin CD11b, an increase in the expression of sialyl Lewis( x) (CD15s) and the hyaluronate receptor (CD44) as well as a significan t decrease in L-selectin (CD62L) expression. Separated neutrophils are also more resistant than unseparated neutrophils to PMA induced upreg ulation of a functional epitope of CD11b. Incubating neutrophils at 37 degrees C is associated with increases in the expression of structura l and functional epitopes of CD11b. Neutrophil separation is also asso ciated with increases in the expression of both structural and functio nal epitopes of CD11b which is greater when neutrophil separation is p erformed at room temperature compared with neutrophil separation at 0- 4 degrees C. However, this difference is lost when the latter are incu bated at. 37 degrees C. Furthermore, neutrophil separation at both 0-4 degrees C and room temperature is associated with a significant incre ase in CD15s expression. This increase is less when separation is perf ormed at room temperature. These findings suggest that neutrophil sepa ration should be performed at room temperature unless the cells are go ing to be used at 0-4 degrees C. Researchers using purified neutrophil populations need to be aware of these significant structural and func tional changes when extrapolating in vitro results to in vivo situatio ns.