Table 4.

Spearman rank correlation between metabolites in the kynurenine pathway and selected cytokines

	Tryptophan (μM)	Kynurenine (nM)	Quinolinic acid (nM)	Kynurenine/tryptophan
IP-10	−0.09	0.39	0.43	0.43
TNF-α	−0.13	0.45	0.49	0.48
IL-16	−0.08	0.43	0.40	0.40
IL-6	−0.12	0.15	0.07	0.19
MIP-1β	−0.17	0.15	0.07	0.24
IFN-γ	0.03	0.17	0.29	0.12

Spearman’s correlation coefficients (r_s) above |0.2| are highlighted in bold.

IFN-γ, interferon gamma; IL, interleukin; IP-10, interferon gamma-induced protein 10; MIP-1β, macrophage inflammatory proteins 1 beta; TNF-α, tumour necrosis factor alpha.