To determine if D . scandens could account for the induction of cytokines , supernatants from the cultured PBMC were tested for IL-2 and IL-4 secretion . Owing to the limited number of PBMC obtained , we could perform on only four donors whose PBMC were also used to assess for lymphocyte proliferation and NK cell activity . The supernatants of 2 donors could be collected on days 1,3 and 5, while those of the other two donors could be harvested only on day 1 and day 3.