Toll-like receptor 2 and P. acnes: do they trigger initial acne vulgaris lesions?

To elucidate the role of toll-like receptor 2 (TLR2) in the pathogenesis of acne vulgaris through its immunohistochemical localization in inflammatory and noninflammatory lesions of this disease entity.

Using standard immunohistochemical techniques, we examined 30 acne cases (involved and noninvolved skin) and the normal skin biopsies of 30 sex- and age-matched, healthy subjects representing the control group.

All examined cases showed positive TLR2 expression in epidermis, pilosebaceous units and dermal inflammatory infiltrate. There were statistically significant differences between acne-involved skin and normal skin and between acne-involved and noninvolved skin regarding TLR2 expression intensity in pilosebaceous units (p < 0.001 for both) and dermal inflammatory infiltrate (p < 0.001 for both). Intense TLR2 expression was in favor of inflammatory acne lesions in pilosebaceous units (p = 0.03) and dermal inflammatory infiltrate (p < 0.05). Intense TLR2 expression was also in favor of severe acne lesions in pilosebaceous units (p = 0.0002) and dermal inflammatory infiltrate (p = 0.001).

TLR2 is involved in the pathogenesis of inflammatory and noninflammatory acne lesions. This occurs through Propionibacterium acnes-mediated activation with the resultant release of inflammatory cytokines.