keratinocyte expression of human beta defensin 2 following bacterial infection role in cutaneous host defense human beta defensin 2 hbetad2 is thought to play an important role in cutaneous immune defense we hypothesized that i keratinocyte expression of hbetad2 measured by reverse transcriptionpcr would be upregulated in response to challenge with pathogenic bacteria particularly highly adherent strains of streptococcus pyogenes and staphylococcus aureus and ii hbetad2 would have potent antimicrobial activity against pathogenic but not commensal organisms expression of hbetad2 was induced consistently by s aureus staphylococcus epidermidis escherichia coli and pseudomonas aeruginosa whereas strains of s pyogenes were poor and variable inducers of hbetad2 no correlation was found between levels of bacterial adherence and keratinocyte expression of hbetad2 s pyogenes was significantly more sensitive to killing by hbetad2 than s epidermidis we conclude that the ability to induce hbetad2 expression in combination with sensitivity to its antimicrobial effects may contribute to the rarity of skin infections with the gramnegative bacterial organisms whereas lack of stimulation of hbetad2 expression by s pyogenes may be important in its ability to evade innate defenses and cause skin disease induction of expression of hbetad2 but relative tolerance to it may enable s epidermidis to survive on the skin surface and modulate hbetad2 expression when the stratum corneum barrier is disrupted