FIGURE 1.

1,25D₃ enables supernatants from T cells isolated from psoriatic plaques to increase cathelicidin expression in human keratinocytes. A, Keratinocytes in lesional skin strongly express IL-17RA and cathelicidin peptide as demonstrated by staining of paraffin sections of skin from patients with psoriasis with an IL-17RA and hCAP18/LL-37 Ab, respectively. B, Human keratinocytes (HaCaT) were treated with supernatants from T cells isolated from psoriatic plaques in the presence or absence of 1,25D₃ (10⁻¹¹ M). To block IL-17A signaling, an IL-17RA blocking Ab was added 30 min before stimulation. Cells were harvested after 24 h and cathelicidin transcript levels were analyzed by quantitative real-time PCR. C, In a control experiment, HaCaT keratinocytes were treated for 24 h with 1,25D₃ (10⁻⁸ M), IL-17A (10 ng/ml), or the combination. Cathelicidin transcript abundance was analyzed by quantitative real-time PCR. Data are mean ± SD of a single experiment performed in triplicate and are representative of three independent experiments *, p < 0.05, determined by Student’s t test.