Binding of XXXX recombinant 125I-interferon gamma to receptors on @entity1 cells.

@entity1 @entity3692 @entity1880 @entity379 @entity2391 @entity3027 @entity526
Recombinant @entity1 @entity379 ) produced in @entity526 was labeled with 125I to study its binding to receptors of HeLa and lymphoblastoid cells. All the cell lines examined had receptors for @entity3692 , although the binding varied considerably among different cell lines. The binding of 125I- @entity3692 was competed up to 90% by the addition of unlabeled @entity3692 , although not by the addition of @entity3027 or -beta. By adding increasing concentrations of unlabeled @entity3692 to binding assays containing a constant amount of 125I- @entity3692 , we determined a KD of 3.7 and 6.3 X 10(-10) M for its binding to Daudi and HeLa cells, respectively. About 13,000 receptors per cell were present in Daudi and 5,000 in HeLa cells. The Mr of the @entity379 /receptor complex was determined by cross-linking experiments to be about 125,000. This complex is smaller than the @entity3027 /receptor complex that has a Mr of about 140,000. The @entity3692 receptor was down-regulated when HeLa cells were treated with this interferon, but not when these cells were treated with @entity2391 . These findings suggest that the receptors for @entity3027 and -gamma differ in several characteristics. The turnover of the @entity3692 receptor was measured by inhibiting protein synthesis with @entity1880 and the half-life of this receptor was found to be 2 h. The unglycosylated @entity3692 was bound to cellular receptors with an affinity similar to that previously reported for natural @entity379 . The lymphoblastoid cell lines examined had high affinity receptors for @entity3692 , but did not respond to treatment with this IFN with an induction of the synthesis of the enzyme (2'-5')oligo(A) synthetase, whereas HeLa cells responded to @entity3692 . The reason for the lack of response of lymphoblastoid cells is presently unknown.
