A study on an artifact introduced by fetal bovine serum-supplemented medium.

The antiserum raised in (C3H/HeJ X A/J)F1 mice by repeated immunization with mitomycin c(MMC)-treated ASL-1 leukemia cells maintained in vivo reacted with all tumor and normal cell lines maintained in vitro, but not with cell lines maintained in vivo. The common antigens detected in tissue-culture cells (CATC) turned negative after short in vivo cultivation of in vitro ASL-1 cells, and turned positive after short in vitro cultivation of in vivo ASL-1 cells. Treatment of cultured cells with antibiotics (kanamycin, gentamycin) did not alter the reactivity to the a-CATC serum. However, the activity of a-CATC serum was reduced by mixing the anti serum with fetal bovine serum (FBS), and an antigen antibody precipitation reaction occurred between the serum and FBS. Antigens which reacted with this antiserum were indicated to be FBS-related. The antibody against FBS was incidentally produced by immunization with weakly immunogenic tumor cells treated with MMC in FBS-supplemented medium. This study reinforms that the presence of FBS bound to cell membranes can introduce artifacts in the serological analysis of antiserum.