In utero sensitization with influenza virus in man.

Following a community-wide epidemic of influenza A/England virus infection, 64 cord blood samples were evaluated for their fetal serum and lymphocyte responses to this virus. Cord sera were tested for HI antibody vs. A/England with and without 2-ME. A fourfold or greater reduction in titer was observed in four, indicating fetal IgM antibody responses. In addition, lymphocyte samples from three of 16 tested showed proliferative responses to influenza A suggesting fetal lymphocyte sensitization with influenza virus. These data suggest that, in some pregnancies, influenza virus is capable of transplacental sensitization of the fetus.