Spontaneous rosette formation in vitro under the effect of agents affecting the cyclic nucleotide system of circulating lymphocytes of normal subjects.

Aminophylline was found to effect the early and total rosette-forming capacity of human thymus-dependent lymphocytes. This may be connected with an increase in the intracellular cyclic adenosine 3',5'-monophosphate level. Acetylcholine increases the proportion of early spontaneous rosettes, a phenomenon suggestive of a shift within the lymphocyte population toward a subpopulation of higher activity. The effect of acetylcholine is possibly mediated by an increase in the intracellular cyclic guanosine 3'-, 5'-monophosphate level. Aminophylline affects only the early rosette-forming capacity of thymus-derived lymphocytes. Levamisole has no influence on either early or total rosette-forming capacity of normal lymphocytes. The results are suggestive of definite relationships between the functional state, activity and cyclic nucleotide system of thymus-dependent lymphocytes.