We modelled IgA at two sites in the host: mucosal IgA (IgAm), which is unobserved (other than at post-mortem) and represents local IgA at the site of infection and affects worm length; and plasma IgA (IgAp), which represents the IgA that has migrated to the plasma and can be routinely measured in the bloodstream of live animals. Here, CD79A is linked to infection.