Cotesia plutellae has been known as a natural enemy against the Diamondback moth, Plutella xylostella via laying eggs into a larva. When the larva hatches from the egg, teratocytes also are released and expected to work as immune suppressor via secreting immune suppressive factors such as venom proteins, teratocytes and polydnavirus. In order to identify immune suppressive factors from teratocytes, we collected the supernatant from serum-free culture media of teratocytes. Concentration of secreted proteins from teratocytes was successfully performed with using centricons among tested methods such proteins precipitation and electrophoresed in sodium dodecyl sulfate polyacrylamide gel. The gel slices were directly digested with trypsin using in-gel digestion method and analyzed via LC-Ms-Ms. Molecular weight of peptide fragments were compared with protein database predicted by full-genome sequences of C. plutellae. We identified two immune responsive proteins, which are calreticulin, host cellular response-related gene and neprilysin 2, immune regulator. This result suggests that host immune response is suppressed or regulated by the immune suppressive factors of teratocytes.