Ro 31-9790 inhibits ATP-induced shedding of CD23 and L-selectin. B-CLL lymphocytes were treated with the indicated concentrations of Ro 31-9790 before exposure to 500 μmol/L ATP for 7 minutes for CD23 and 1.5 minutes for L-selectin. CD23 (○) and L-selectin (•) expression was then determined and the results expressed as the mean percentage of inhibition of shedding ±SEM (n = 3). *, P < .05.