Clinical parameters of health and hookworm infection status (11, 54) are combined with measures of the innate and adaptive immune response, including total IgG, lysozyme activity and constitutive gene expression of cytokines IFNγ, IL-6, IL-10 and TNFα in order to characterize the immunological response to hookworm infection in Australian sea lion pups, and to identify developmental trends in immune parameters. The gene discussed is IL10; the disease is ancylostomiasis.