Immunohistochemical studies of proinflammatory cytokines and their receptors in hair follicles of normal human skin.

Immunoreactivity to interleukin-1 alpha, interleukin-1 beta, interleukin-6 and tumour necrosis factor-alpha and their receptors, as well as the endogenous interleukin-1 receptor antagonist, was investigated in hair follicles in paraffin-embedded normal human skin. Interleukin-1 beta- and tumour necrosis factor-alpha-like immunoreactivities were found in the inner root sheath layer of hair follicles, at the suprapapillary level. Interleukin-1 receptor-like immunoreactivity was also found in this layer, while there was a variable immunoreactivity to the interleukin-1 receptor antagonist. In the outer root sheath there was a weak to moderate staining for the four cytokines, in addition to intense staining for their receptors and a weak staining for the antagonist. The fibrous root sheath had a moderate immunoreactivity for interleukin-1 alpha and interleukin-6. The distribution patterns suggest that these cytokines, particularly interleukin-1 beta and tumour necrosis factor-alpha, may have a protective role in hair formation, while all the investigated proinflammatory cytokines may have a role in the differentiation process.