I would like to thank Drs Schulze and Mahrle for their interest in our article. Drs Schulze and Mahrle have found that intralesional injection of recombinant interferon gamma (rIFN-gamma), which results in local lymphokine concentrations sufficient to induce HLA-DR expression by keratinocytes, does not affect the epidermal cytokinetics in the psoriatic plaque. This was supported by their clinical observation that no improvement of the lesion occurred. These data are very stimulating because of their apparent contradiction of the in vitro data on the effect of rIFN-gamma on normal keratinocyte growth.1 Several explanations for this disparity between the in situ and in vitro situation come to mind. First, that the concentration of rIFN-gamma needed for induction of HLA-DR antigen expression is lower than that needed for growth inhibition. Some of our recent in vitro data suggest that this may be the case.2 Second, it is conceivable that the "psoriatic"
Morhenn VB. Recombinant Interferon Gamma in Psoriasis-Reply. Arch Dermatol. 1988;124(4):488–489. doi:10.1001/archderm.1988.01670040008004
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