Splenocytes were washed twice and then
resuspended in RPMI 1640 (Gibco, NY, USA)
supplemented with benzyl-penicillin (100 IU/ml),
streptomycin (100 IU/ml), and 10% fetal bovine serum.
Blood samples with sodium heparin were diluted with an
equal volume of Hanks’ solution and carefully layered on
the surface of the lymphocyte separation medium.