Selected human T cell lines respond to thymopoietin with intracellular cyclic GMP elevations

Ten established human cell lines were tested for their responsiveness to thymopoietin by measuring their intracellular cyclic nucleotide levels. Three T cell lines (CCRF-CEM, MOLT-4 and CCRF-HSB-2) responded to thymopoietin with elevations of intracellular cGMP but not cAMP; seven other human cell lines did not respond to thymopoietin (three T cell lines, three B cell lines and one erythropoietic stem cell line). Interestingly, only one cell line (MOLT-4) was also responsive to the closely related polypeptide splenin, and this reactivity was restricted to human and not bovine splenin. The detection of human cell lines with distinctive patterns of response to immunoregulatory peptides should provide support for understanding the immunopharmacological mechanisms by which these molecules act.