Effects of infection and its interaction with housing on changes in antibody titers after infection After infection with PRRSV, delta PC-BSA-IgM (delta 46-44, 48–44, and 52–44) tended to be affected by the interaction between infection and housing (F(1.52) = 3.1, P < 0.10), by delta-day (F(2.99) = 19.5, P < 0.001) and by the housing × infection × delta-day interaction (F(2.99) = 2.9, P < 0.10). Here, CD40LG is linked to infection.