Control of immunoglobulin isotype production by porcine B-cells cultured with cytokines

Cytokines regulate immunoglobulin (Ig) isotype production following the Th1/Th2 paradigm, derived from studies of inbred mice. In pigs, it is not known which, if any, Ig isotypes may reflect a Th1/Th2 response. To evaluate this, purified porcine CD21+ B-cells were co-cultured with Staphylococcus aureus Cowan strain 1 or Escherichia coli lipopolysaccharide as B-cell mitogens together with recombinant human IL-2, and recombinant porcine (rp) interferon (IFN)-γ, IL-12 or IL-10. While the mitogens increased B-cell proliferation, cytokines had no additional effect. A quantitative competitive enzyme-immuno assay was used to measure concentrations of porcine IgM, IgG1 and IgG2 in B-cell culture supernatants. In vitro, porcine B-cells produced IgG2, 106±17.3 μg/ml; IgG1 107±38.3 μg/ml and IgM 25.6±8.45 μg/ml. In some individuals, Th1 cytokines such as rpIFN-γ and IL-12, enhanced IgG2 in the face of low concentrations of IgG1. Furthermore, individual responses, in some cases, tended to be diametrically opposed, reminiscent of previously documented categorical immune responses in pigs such that some individuals produced high concentrations of IgG1 in response to the various doses of rp cytokines, while others produced lower concentrations. Pigs may generate a high IgG1:IgG2 ratio in response to rpIL-10, and possibly to other Th2-associated cytokines. However, B-cell response to rp cytokines in vitro exhibits marked variation by pig, a feature that is likely a function of highly variable individual genotypes and their interaction with complex environments.