Thymulin is a nonapeptide produced by two distinct epithelial populations in the thymus first described by Bach in 1977. It requires zinc for biological activity.The hormone is believed to be involved in T-cell differentiation and enhancement of T and NK cell actions. Besides this rather paracrine or auto-organic effects on the thymus dependent immune system, Thymulin seems to have neuroendocrine effects as well. There exist bidirectional interactions between thymic epithelium and the hypothalamus-pituitary axis (for example, thymulin follows a circadian rhythm and physiologically elevated ACTH levels correlate positively with thymulin plasma levels and vice versa).A recent focus has been on the role of thymulin as an effector on proinflammatory mediators/cytokines. A peptide analog of thymulin (PAT) has been found to have analgesic effects in higher concentrations and particularly neuroprotective anti-inflammatory effects in the CNS.
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