Immune responses of periodontal tissue may be regulated by products of sensory afferent nerve endings such as neuropeptides. Substance P (SP) , a tachykinin neuropeptide, has been previously reported to stimulate the activities of T lymphocyte. Therefore, I examined the role of SP in IL2 production and cell proliferation by using a homogeneous line of T lymphocytes (Jurkat and HuT78). Cell proliferation rate was determined by [3H]-thymidine incorporation test, and IL-2 was quantitated by the growth rate of CD4+ IL-2-dependent T lymphocyte line CTLL-2.
SP stimulated cell proliferation of T lymphocytes at the concentration of 10-12 and 10-8M in a biphasic bell-shape dose-dependent manner. However, SP alone did not induce IL-2 release at the concentration range of 10-6 to 10-14M. The upregulation of IL-2 release was observed when 10-12M SP was applied together with mitogens such as Con A or PHA+PMA on T cell lines, especially on Jurkat. Con A or PHA+PMA demonstrated to increase the rate of cell proliferation of Jurkat, which had shown to produce much amount of IL-2 indicating that mitogen-induced cell proliferation might be partially influenced by released IL-2. It was concluded that regulatory effects of SP on the immune/inflammatory response could be mediated through the costimulatory upregulation of IL-2 production and increase of cell proliferation of T lymphocyte.
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