Chick sympathetic neurons in culture respond differentially to nerve growth factor and conditioned medium from activated splenic lymphocytes.

Chicken splenic cells, stimulated by concanavalin A, secreted a factor or factors into the culture medium which supported the survival of neurons from sympathetic ganglia of chick embryos. The effect of this conditioned medium (CM) was similar to the effect of nerve growth factor (NGF). However, the enhanced survival effect of CM was unaffected by K-252a, a protein kinase inhibitor which completely abolished the effect of NGF. 6-Thioguanine, an inhibitor of NGF-activated protein kinase N, blocked the survival effects of both NGF and CM on sympathetic neurons, but a dose required for the half-maximal inhibition for the survival effect of CM was 10 times higher than that for NGF. H-7, an inhibitor of protein kinase C, did not block the effect of either CM or NGF. On the other hand, the survival effect of both CM and NGF was blocked to the same extent by 5'-deoxy-5'-methylthioadenosine and LiCl. These results suggest that activated splenic cells secreted neuronal survival-promoting factor(s) into CM and that the cellular mechanisms promoting neuronal survival by CM are different from those promoting neuronal survival induced by NGF.