PTGDS and systemic lupus erythematosus: However, PTGDR-2 expression was increased on basophils from patients with SLE (Table 1 and Fig. 1b, c) as did PTGDR-1 and PTGDR-2 mRNA levels (Fig. 1d–f) and their ligand titers in SLE patient plasma (represented by levels of 11β-PGF2α, the main specific plasmatic PGD2 metabolite30) (Fig. 1g).