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 h uman inflammatory acne, were studied. Pigs were chosen as experimental anim als because their skin is similar in structure and composition to that of m an 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 wee ks later with doses ranging from 1-100 mu g of HKPA in various intradermal sites on the ventral aspect of the abdomen. Four further pigs, previously s ensitized with Bacillus Calmette-Guerin (BCG) but not HKPA, were challenged with purified protein derivative (PPD) of bovine tuberculin and HKPA. Entr y of Cr-51-labelled peripheral blood lymphocytes (PBLs) over 48 h was studi ed in all the challenge sites. Peak PBL entry occurred at 4 h, remaining su stained 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 PP D-challenge sites in HKPA-sensitized pigs or in HKPA-challenged sites in BC G-sensitized Digs. There was also a substantial influx of (111)Indium-label led neutrophils into the lesions. Lymphocytes present were predominantly of the CD3(+)CD2(+) T-cell subset, although gamma delta TCR+ cells were prese nt also, particularly after 24 h. E-selectin was markedly upregulated on de rmal endothelium in the P. acnes sites. The histological infiltration and k inetics were similar to those reported in human inflammatory acne. (C) 2000 Harcourt Publishers Ltd.