CD24 EXPRESSION ON HUMAN KERATINOCYTES

CD24 or Nectadrin is a cell surface glycoprotein expressed in pre-B ly mphocytes, T lymphocytes, neurons, muscle cells and carcinoma cells. I ts function is not completely known, but it has been suggested that it is involved in cell adhesion and signalling. CD24 has recently been i dentified as the human molecule homologous to the murine heat-stable a ntigen (HSA). HSA is expressed by murine keratinocytes and delivers co stimulatory signals in T-cell activation. Long-term cultures of normal human keratinocytes (HKC) were obtained from skin of human female bre ast sections and either left untreated or were treated with phorbol-12 -myristate-13-acetate (PMA) at 10-100 ng/ml, calcium 0.5-2 mM or IFN-g amma 100-1000 U/ml, for 24-48 h. Using RT-PCR and flow cytometry we sh owed that HKC express low levels of CD24 even under basal conditions, and the treatment with calcium, PMA or IFN-gamma increased levels of C D24 mRNA and protein. To the best of our knowledge, this is the first report to measure CD24 expression and production by cultured HKC in ba sal conditions and after stimulation. Further studies are needed to de termine biological and therapeutical relevance of these findings.