On day 4 all the mice were injected
with 0.9% saline solution (10 ml/kg, i.p.) by gentle massage. The
peritoneal fluid was collected after five min and transferred into a
test tube containing 7–10 ml RPMI-1640 (Roswell Park Memorrial
Institute) buffer medium (pH 7.2–7.4), composed of l-glutamine
and 25mM Hepes buffer without sodium bicarbonate.