[en] Therapeutic concentrations of acetylsalicylic acid (ASA) have strikingly inhibited in vitro and in vivo mitogen- and antigen-induced blastogenesis by human lymphocytes. These observations may be pertinent to the anti-inflammatory actions of ASA. To investigate further the possible effects of ASA on cellular responses, a study was made of the in vitro interactions of [¹⁴C]ASA with lymphocytes. Results indicated that the [¹⁴C]ASA association with cells was (a) proportional to ASA concentrations, (b) non-saturable at high concentrations of ASA, (c) dependent on pH, (d) independent of temperature, (e) dependent on cell concentration, (f) not consistently displaced by unlabelled ASA or other drugs, (g) rapid and unchanged over 1 min to 72 hr incubations and (h) reversed by repeated cell washing. These data confirmed that ASA indeed interacted with lymphocytes. The association was rapid, reversible, pH-dependent and not demonstrably specific under these experimental conditions. (author)