CpG motifs induce Langerhans cell migration in vivo

Cytosine-guanosine (CpG) oligonucleotide (CpG-oligo) sequences are immunost imulatory motifs that are present in bacterial DNA and their presence in pl asmids might contribute to the immune response generated by DNA vaccination . The cell targets of CpG motifs in vivo have not been characterized yet. I n this report we assessed the in vivo effects of CpG motifs on Langerhans c ells (LC) migration. We showed that intradermal injection of 10 mu g of CpG -containing oligonucleotides in mouse ear Induced the local depletion of LC within 2 h of exposure as shown by CD11c and la immunohistological stainin g. To demonstrate that LC depletion was due to LC migration, CpG oligonucle otides were injected into the explants ex vivo, and the CD11c(+) cells emig rating from the cultured isolated skin within medium were evaluated by immu nostaining and FAGS analysis. Our findings demonstrate that CpG motifs indu ce LC/dendritic cell (DC) migration out of the skin. To assess whether CpG motifs may act directly on LC/DC to induce their emigration we next analyze d the effects of CpG motifs in vitro on the expression of adhesion molecule s involved in LC/DC migration. The results of these experiments show that a lpha(6) integrins, E-Cadherin, ICAM-1, CD11b and CD11c were differentially regulated upon CpG-oligo treatment of immortalized DC. CpG treatment (10 mu g/ml for 8 h) resulted in a 100% increase in ICAM-1 staining intensity, a 50% decrease in E-Cadherin staining and a 25% decrease in alpha(6) integrin s staining, while no changes in the levels of CD11b and CD11c expression we re recorded. Changes in adhesion molecule expression were mirrored by conco mitant changes in the cell morphology that included cell depolarization, th e appearance of filopods and loss of adherence. This study provides the fir st in vivo evidence that CPG motifs signal the migration of LC from the epi dermis.