Leucocyte entry and endothelial E-selectin expression following intradermal Propionibacterium acnes administration

Area of Science:

• Dermatology
• Immunology
• Microbiology

Background:

• Propionibacterium acnes (P. acnes) is a major bacterial agent implicated in human inflammatory acne.
• Porcine skin shares structural and compositional similarities with human skin, making pigs a suitable model.
• Genetically inbred pigs allow for leucocyte transfer without rejection, facilitating immune response studies.

Purpose of the Study:

• To investigate the immune responses in porcine skin following intradermal inoculation of heat-killed P. acnes (HKPA).
• To characterize the cellular infiltrate and endothelial changes in response to HKPA challenge.
• To compare the induced immune response with that observed in human inflammatory acne.

Main Methods:

• Intradermal inoculation of heat-killed P. acnes (HKPA) in sensitized pigs.
• Dose-ranging challenge with HKPA and purified protein derivative (PPD) in control pigs.
• Tracking of chromium-51 (51Cr)-labeled peripheral blood lymphocytes (PBLs) and indium-111 (111In)-labeled neutrophils.

Main Results:

• Peak PBL entry into challenge sites occurred at 4 hours, sustained up to 24 hours.
• HKPA induced a dose-dependent and antigen-specific influx of PBLs and neutrophils.
• Predominant lymphocyte subset was CD3(+)CD2(+)T-cells, with gammadelta TCR(+)cells noted later; E-selectin was upregulated on dermal endothelium.

Conclusions:

• The porcine model effectively mimics human inflammatory acne immune responses.
• HKPA triggers a specific, dose-dependent inflammatory infiltrate involving lymphocytes and neutrophils.
• Upregulation of E-selectin suggests a role for endothelial adhesion molecules in P. acnes-induced skin inflammation.