Overall antibody response Overall, KLH-IgM titers were not affected by housing or infection, but only by sampling day (F(6.307) = 90.8, P < 0.001), with increasing titers from day 38 to 52 (only day 44 and day 46 titers did not differ), but after infection with A. pleuropneumoniae on day 52, levels of KLH-IgM remained stable (Figure 1A). Here, CD40LG is linked to infection.