Figure 3. IL7Rα Hap 4 is less responsive to IFNβ than Hap 1 or Hap 2 in myeloid cells of heterozygous Hap 4 carriers.

(A) Freshly purified monocytes (mono), myeloid dendritic cells (mDC) and plasmacytoid dendritic cells (pDC) and in vitro cultured immature (IL-4, GM.CSF; iDC) or maturing monocyte-derived dendritic cells (IL-4, GM.CSF, LPS; matDC) from healthy control heterozygous carriers of Hap 4 (n = 3, each in triplicate, except for pDCs, each in duplicate) were incubated +/− IFNβ (1000 IU/ml; with the exception of pDCs at 2000 IU/ml) for 24 h. Subjects were heterozygous carriers of Hap 4, bearing either Hap 1 or Hap 2 as the other allele. Expression of each haplotype was measured using tagging SNPs as previously described [13] and is presented as a ratio of expression of Hap 4/Not Hap 4 (i.e. Hap 4/Hap 1 or Hap 4/Hap 2) for each individual. In response to IFNβ, Hap 4 was expressed at a relatively lower level in all subsets than in the absence of IFNβ. Mean +/− SEM is shown; *significantly different from media condition by paired t test (mono, p = 0.025; iDC, p = 0.0003; mDC, p = 0.012; pDC, p = 0.022; mat DC showed a trend, p = 0.052). Monocytes from healthy control (n = 5) (B) or MS (n = 5) (C) heterozygous carriers of Hap 4 were purified from thawed cryopreserved PBMCs, differentiated into iDC or mDC and treated with IFNβas above. No differences in haplotype response were seen between MS and controls. A significant proportion of the combined cohort from frozen cells (n = 10; healthy control + MS) decreased relative expression of Hap4 in response to IFNβwhen all cell subsets were included in the analysis (p = 0.043, sign test); this did not reach significance for individual groups or cell subsets.