FIG 3.

Immunofluorescence localization of ACE2 and TMPRSS2 proteins in the trophoblasts of human placental villi. (A and B) The human placenta villous sections were immunostained with antibodies to ACE2 (A) and TMPRSS2 (B). The concentrations of each pair of specific and control, nonspecific IgG (rIgG), were identical. All image acquisition parameters and intensity scales were identical for each pair of specific and nonspecific antibodies. The panels represent three independent experiments. Bars, 10 μm. (C) Western blot of TMPRSS2 in primary human trophoblasts (PHTs). Whole-cell lysates of PHT cells (60 μg), derived from nine independent placentas, were resolved on SDS-PAGs and transferred to PVDF membranes that were blotted in three independent Western immunoblots using a mouse anti-TMPRSS2 antibody as detailed in Materials and Methods. Note that TMPRSS2 is expressed as a full-length zymogen protein (∼70 kDa) and is processed by proteolytic cleavage (89, 90), producing three activated mature forms with a smaller size (∼37 kDa), derived from two isoforms.