CD79A and infection: In terms of other interactions with the host immune system, no Tci-Prx1-specific serum IgG or serum IgA was present in the sera of lambs which had been exposed to an extended trickle infection of T. circumcincta, though antigen-specific IgG and IgA against ES proteins, Tci-MEP-1 and Tci-APY-1, was present in these lambs.