The predictions of the model were tested by analysing the effect of the interaction between age and infection intensity on anti-Sh13 IgG3 levels which was significant (F = 3.604, df = 3, 147, p = 0.015), so that the relationship between anti-Sh13 IgG3 levels and infection intensity varied depending on the age of the participant. Here, IGHG3 is linked to infection.