1. Both adenosine 3′:5′-cyclic monophosphate and guanosine 3′:5′-cyclic monophosphate phosphodiesterase activities of peripheral blood mononuclear cells were markedly decreased in elderly women as compared with young control women.
2. In contrast, the ability of these cells to bind guanosine 5′-[β, γ-imido]triphosphate, a non-hydrolysable analogue of guanosine 5′-triphosphate, was the same in both groups.
3. These findings are discussed in the context of the decline in immune function which occurs with increasing age.