An homologous in vitro assay to detect lymphokines released by PHA-activated duck peripheral blood lymphocytes and spleen cells.

When stimulated with phytohaemagglutinin duck lymphocytes released lymphokines which were detected by their ability to maintain the proliferation of duck lymphoblasts using an in vitro assay similar to that previously developed with the mammalian system to measure IL-2. The inability of duck lymphokines to maintain the proliferation of mammalian lymphoblasts (mouse) indicated that there was no functional homology between duck and mammalian lymphokines. However, duck lymphokines did maintain the proliferation of chicken lymphoblasts indicating functional homology of these growth factors between these two species. The duck lymphokine maintenance assay is a simple and reliable test, and should be useful as an in vitro assay for the detection of factors released by antigen-specific lymphocytes when cultured in the presence of viral antigens.