IL17A and depressive disorder: Furthermore, we found that mice receiving fecal transfer of depressed patients had increased levels of Segmented filamentous bacteria (SFB) (Fig. 6A), of intestinal Il-17a (Fig. 6B), and increased levels of serum amyloid A (SAA)2 (Fig. 6D), while they show no difference in the level of SAA1 and SAA3 (Fig. 6 C and E), which corroborated our previous findings that the axis SFB/SAA2/Th17 is activated in depression [31].