Figure 6. Viral inflammation drives thrombocytopenia and serotonin turnover.

(A) Cartoon of serotonin transport and degradation.

(B–G) Platelet counts in naive or VSV-infected mice (B); LCMV CL13-infected mice at day 15 post-infection (C); and poly(I:C)-treated wild-type (D), TLR3^−/− (E), anti-IFNAR-receiving (F), and STAT1^−/− mice.

(H–L) Mean platelet volume of VSV-infected mice (H) and poly(I:C)-treated wild-type (I), TLR3^−/− (J), anti-IFNAR-receiving (K), and STAT1^−/− mice (L).

(M) Plasma serotonin in mice treated with a platelet-depleting antibody.

(N–Q) Representative FACS plot (N and P) and quantification (O and Q) of platelet CD62P expression (N and O) and platelet aggregation (P and Q) in poly(I:C)-treated mice.

(R and S) Prothrombin (R) and partial thromboplastin (S) time in poly(I:C)-treated mice.

(T–V) Ileal Maoa expression in mice treated with SARS-CoV-2 (USA-WA 1/2020) (T), VSV (U), or poly(I:C) (V).

(W–Z) 5-HIAA levels in urine from mice infected with VSV (W) and LCMV ARM or CL13 at day 15 post-infection (X), as well as poly(I:C)-treated wild-type (Y) and STAT1^−/− mice (Z).

(AA) Platelet serotonin levels of poly(I:C)-treated mice receiving the MAO inhibitor phenelzine.

Plotted are means ± SEM. n.s. p > 0.05, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. See also Figure S6.