The spleens were aseptically removed and transferred to culture dishes containing 2 ml of cold HBSS. Forceps and carbasus were used to finely triturate the spleens, then the cell suspensions were transferred to tubes and washed twice in HBSS and centrifuged for 10 min at 1000 rpm at 4°C. Splenocytes were resuspended in 3 ml of appropriate culture medium (Roswell Park Memorial Institute, RPMI, 1640 medium with phenol red supplemented) (Gibco, Grand Island, NY, USA). Cell numbers were determined for each splenocyte suspension by counting in a hemocytometer and cell viabilities were verified by trypan blue exclusion method.