Bovine J blood-group activity in the lipids of erythrocytes of different age.

J-positive cattle erythrocytes were separated according to age by ultracentrifugation in a discontinuous density gradient of Ficoll-400 (Pharmacia) in isotonic buffer solution. A decrease in phospholipid and in cholesterol content with increasing age was detected. The J activity was found to increase markedly with increasing cell age. This fact supports the view that the in vivo transfer of the J determinant from plasma to erythrocytes is a rather slow process. It is suggested that the increasing J activity of older cells is probably due to a decrease of erythrocyte membrane bound phospholipids which inhibit the transfer of the J determinant to the red cells.