Fig. 1. Target engagement of Ab4B19 in ovarian follicles.

a Immunofluorescence staining of ovarian follicles showed that Ab4B19 penetrated across BFB and co-localized with the AMH-positive granulosa cells in ovarian follicles. Ovaries were collected for immunostaining 48 h (48 h) after tail vein injection of Ab4B19 into adult mice. The rabbit monoclonal antibody Ab4B19 was detected with anti-rabbit IgG (FITC, green). AMH was probed with mouse anti-AMH and detected with anti-mouse IgG (TRITC, red). Cell nucleus were labeled with DAPI (blue). White arrows indicate the presence of Ab4B19 in ovarian follicles. Scale bar, 100 and 50 μm (the high magnification). Experiments were repeated three times independently with similar results (four sections/mice each time). b Time course of TrkB activation in the ovary, revealed by Western blots, after Ab4B19 administration (1 mg/kg; iv) into 8-week-old mice. Ovary tissues were collected and lysed at different time points after tail vein injection of Ab4B19, and pTrkB, pAkt, and pERK were analyzed. c Quantitative plots of TrkB activation and its downstream signaling (pAkt/Akt, pERK/ERK) at 48 h. N = 4 mice in the vehicle group and 5 mice in the Ab4B19 group, with the same samples repeated at least twice (n = 10). d Pharmacokinetics of Ab4B19 in plasma (left) and ovary tissues (right). Ab4B19 was administered into mice (2 months old, 1 mg/kg) by tail vein injection, its concentrations in ovary and plasma at different time points were analyzed by ELISA, and plotted against time (N = 3 mice per time point). Data were presented as mean ± SEM. Statistical analyses were carried out by two-tailed student’s t-test (*P < 0.05; **P < 0.01; ***P < 0.001). Vehicle: normal IgG injected. Source data are provided as a Source Data file.