Studies on cell binding and internalization of human lymphoblastoid (Namalva) interferon

Effect of interferon on Vero cells persistently infected with Sendai virus compared to Vero cells persistently infected with SSPE virus

Persistent infections with Sendai and SSPE virus were established in Vero cells. Sequential passages of these cells were monitored by immunofluorescence and for their sensitivity to the antiviral and antiproliferative effects of interferon (IFN). The cells rapidly developed resistance to the antiviral effect of IFN as judged by the inability of IFN to inhibit the replication of exogenous Sindbis virus. This decrease was accompanied by a reduction in the induction of the 2'-5' oligo A synthetase. Both cell lines were resistant to the antiproliferative effect of IFN. A decrease or absence of IFN receptors on the surface of the cells was not found to be the cause of their resistance to IFN.

A second look at the second messenger hypothesis

Several hundred hormones, neurotransmitters, growth factors and other "first messengers" bind to specific cell membrane receptors and induce a myriad of effects: short term, transport, metabolic, mitotic and regulation of thousands of specific genes. Yet, less than a dozen "second messengers" have been clearly established to date. Even allowing for the discovery of a large number of additional second messengers, there remains a paradox in terms of information-transfer within the cell: how can so many specific signals produce so many effects through so few relatively nonspecific intermediates? We consider several possible solutions to this paradox, including the hypothesis that signal specificity is encoded in part in the primary structure of the receptor.

Corticosteroids modulate the binding of recombinant interferons alpha and gamma in Namalva cells

To investigate possible mechanisms of interaction between corticosteroids and interferons (IFNs), the specific binding of recombinant human IFNs alpha 2 and alpha in Namalva cells after 72 h culture with dexamethasone (10(-8) M to 10(-6) M) was evaluated. Exponentially growing cells were incubated with different concentrations of the radiolabelled IFNs, with or without an excess of unlabelled IFN. The parameters of the interaction between each IFN and its specific receptor were analyzed by the Scatchard method. In the dose range tested, dexamethasone induced a dose-dependent inhibition of Namalva cells growth, which reached about 35% at 10(-6) M. The specific binding of IFN-alpha 2 was decreased to a maximum of 40%, for dexamethasone concentrations greater than or equal to 10(-7) M. The decrease in binding induced by the corticoid was additive with the down-regulation induced by IFN-alpha 2 itself. On the contrary, the specific binding of IFN-alpha was increased by dexamethasone in a dose-dependent fashion within the tested range. The maximal increase in the number of sites per cell was about 60%, with a slight decrease in affinity. These results suggest that complex interactions might arise between corticosteroids and IFNs in the course of their clinical use.