By characterizing the gene expression of 50 primary human keratinocyte cell lines under different culture conditions, it was apparent that in vitro culture with psoriasis-associated cytokines (TNF and IL-17A) increased the expression of SPTLC2 (Supplemental Figure 9), which matched the expression pattern of this gene in psoriasis lesional skin (Figure 9A). This evidence concerns the gene SPTLC2 and psoriasis.