tokens: Antibodies used for analysis of surface markers included : FITC - conjugated rat anti - mouse CD45R / B220 ( RA3 - 6B2 , BD Pharmingen San Diego , CA ) for B cells ; FITC - conjugated rat anti - mouse CD8 alpha ( 53 - 6 . 7 ) and CD4 ( GK1 . 5 , BD Pharmingen , San Diego , CA ) for CD8 + or CD4 + cells , respectively .