Immune responses to EBV. IgM (A) and IgG (B) responses to EBV infection in 6 healthy rabbits (Rbt 415–420) over a period of 7 weeks post infection. Generally, IgM levels were elevated in the first week post-infection and then tailed off by week 5. In contrast, IgG levels gradually increased and remained high up to the 7 weeks follow up. In one rabbit (Rbt 419), both the IgM and IgG responses to EBV were delayed compared to the other animals, peaking at week 4 for IgM and week 7 for IgG (C). The data presented here is for plasma at dilution 1/100. Similar patterns were seen with plasma diluted 1/200 and 1/400, but with lower OD values.