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

Immune responses in porcine skin to intradermal inoculation of heat-killed Propionibacterium acnes (HKPA), the major bacterial agent associated with human inflammatory acne, were studied. Pigs were chosen as experimental animals because their skin is similar in structure and composition to that of man and because the use of genetically inbred pigs enables leucocytes to be transferred between animals without eliciting rejection responses. Two pigs were sensitized intradermally with 10 mg of HKPA and were challenged 2 weeks later with doses ranging from 1-100 microg of HKPA in various intradermal sites on the ventral aspect of the abdomen. Four further pigs, previously sensitized with Bacillus Calmette-Guérin (BCG) but not HKPA, were challenged with purified protein derivative (PPD) of bovine tuberculin and HKPA. Entry of(51)Cr-labelled peripheral blood lymphocytes (PBLs) over 48 h was studied in all the challenge sites. Peak PBL entry occurred at 4 h, remaining sustained up to 24 h. There was a dose-dependent effect of HKPA on the level of PBL entry, which was antigen-specific, as few leucocytes were seen in PPD-challenge sites in HKPA-sensitized pigs or in HKPA-challenged sites in BCG-sensitized pigs. There was also a substantial influx of(111)Indium-labelled neutrophils into the lesions. Lymphocytes present were predominantly of the CD3(+)CD2(+)T-cell subset, although gammadelta TCR(+)cells were present also, particularly after 24 h. E-selectin was markedly upregulated on dermal endothelium in the P. acnes sites. The histological infiltration and kinetics were similar to those reported in human inflammatory acne.