Background: The inflammation in acne vulgaris is widely thought to be induced by an immunological reaction, but the role of Propionibacterium acnes is unclear.
Objectives: To examine the local host response mechanism of a keratinocyte cell line 3 h and 6 h after stimulation with viable and heat-killed P. acnes.
Methods: The quantitative expression of cytokines was measured at the mRNA level by real-time reverse transcription-polymerase chain reaction.
Results: The coincubation of a keratinocyte cell line with viable, but not heat-killed, P. acnes modulated an adequate cytokine response for interleukin (IL)-1beta, granulocyte/macrophage colony-stimulating factor and IL-8. High-performance liquid chromatographic analysis of the in vivo porphyrin pattern secreted by P. acnes revealed a predominance of coproporphyrin III in acne lesions. This same porphyrin fraction also modestly induced IL-8 expression by keratinocytes.
Conclusions: This cytokine pattern may favour a chemotactic response and implicates P. acnes and coproporphyrin III in the recruitment of inflammatory cells to the site of infection and in the development of acne lesions.