Figure 7. Viral infection augments LPS-induced FM IL-1β through inhibition of the TAM receptor pathway.

(A) Human FM explants were treated with no treatment (NT), LPS (100ng/ml), MHV-68 (1.5×10⁴/ml PFU) or both MHV-68 and LPS in the presence of media or rGas6 (50ng/ml). (i) IL-1β secretion in supernatants was measured by ELISA (n=6). Lysates were evaluated by Western blot for expression of (ii) pro-IL-1β and (iii) active IL-1β. Bar charts show pro- and active-IL-1β expression as determined by densitometry and normalized to β-actin (n=4–5) *p<0.05 relative to the NT control unless otherwise indicated. (B) Human FM explants were treated with or without LPS (1ng/ml) in the presence of blocking anti-TAM Abs or isotype control Abs. IL-1β secretion was measured and levels expressed as LPS-induced fold change (FC) relative to the NT control (n=4; *p<0.05 relative to the isotype control). (C–D) Pregnant wildtype or AXL^−/−MERTK^−/− mice were injected on E15.5 with either PBS or LPS (20µg/kg). After 6hrs mice were sacrificed. The FMs were harvested and homogenized for RNA. (D) TYRO3, AXL, MERTK, GAS6 and PROS1 mRNA expression levels in FMs from PBS treated wildtype mice (n=3) were measured by qRT-PCR. (E) IL-1B mRNA expression levels in FMs from PBS and LPS treated wildtype or AXL^−/−MERTK^−/− mice were measured by qRT-PCR. *p<0.05 relative to the control groups unless otherwise indicated. Data are expressed as mean±SEM.