ACVR2B and infectious otitis media: Similarly, activin type IIB receptor (Fig. 3; left column) and follistatin (Fig. 4; left column) were significantly increased in the S-AOM (264.4 ± 31.3; P = 0.007 and 318.8 ± 38.7; P = 0.002, respectively) and L-AOM (357.2 ± 36.4; P = 0.008 and 347.7 ± 32.8; P = 0.005, respectively) groups compared with controls (116.6 ± 26.7 and 237.6 ± 32.2, respectively).