Antigenic cross-reactivity between media supplements for cultured keratinocyte grafts

Patients who were grafted with cultured human keratinocytes have been shown to make antibodies to the xenogeneic proteins, which supplement the culture media. An immune response to these antigens may lead to late graft loss or accelerated rejection of subsequent cultured keratinocyte grafts. Methods to eliminate this potential problem include growing cells in a serum-free medium with bovine pituitary extract as a serum substitute. To determine whether bovine pituitary extract would be subject to an immune response similar to that which is evoked by fetal bovine serum, we investigated their antigenic cross-reactivity. When compared by sodium dodecylsulfate-polyacrylamide gel electrophoresis, considerable similarity was identified between the two supplements. Immunostaining with antibodies to both bovine pituitary extract and fetal bovine serum confirmed antigenic cross-reactivity. Inhibitory enzyme-linked immunosorbent assay studies demonstrated specific cross-reactivity that ranged from 60% to 68%. When tested for antibody cross-reactivity to bovine pituitary extract, serum samples from five patients who were receiving human-keratinocyte grafts that were grown in fetal bovine serum-supplemented media and that exhibited a positive antibody titer to fetal bovine serum showed cross-reactivity that ranged from 30% to 141%. Bovine pituitary extract contains proteins that cross-react with fetal bovine serum. Human keratinocytes that are cultured in media that is supplemented with bovine pituitary extract would therefore be subject to an immune response similar to that which is evoked by human keratinocytes that have been cultured in fetal bovine serum.