Second messengers for thymic hormones

Several indirect arguments have suggested that cyclic AMP (cAMP) may be a second messenger for thymic hormone action. These include the observations that cAMP in the Bach-Dardenne bioassay acts synergistically upon rosette-forming cells with thymulin (Bach and Bach, 1973). In addition, the inductive effects of thymic hormones can readily be mimicked by a variety of products that increase cellular cAMP and conversely can be inhibited by products that decrease cAMP (Scheid et al., 1973, 1975 Astaldi et al., 1978). 

From the second messenger studies performed to date, it can be concluded that a number of candidates exist for intermediates of thymic hormone action. However, it is clear that the intermediate events by which thymic factors induce T cell differentiation are complex and no doubt involve a wide spectrum of mechanisms. The most important of these still remain to be defined. 

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