MBP and infection: After infection with A. pleuropneumoniae, there was no infection effect on MBP-IgM deltas (delta 53–52, 54–52), but only of the interaction between housing and delta-day (F(1.50) = 9.9, P < 0.01), with a lower decrease in titers from delta 54–52 than from delta 53–52 in barren pigs only (Figure 2C).