Lymphokine production and lymphocyte transformation by human mononuclear cells in a serum-free medium

In order to study the effects of purified serum proteins, such as complement components, on human lymphoid cell functions, we have developed a serum-free culture medium that supports lymphocyte transformation and lymphokine production. The medium is comprised of RPMI 1640 containing commercially available purified human serum albumin (HSA). Optimal proliferative responses to mitogens and antigens were noted at HSA concentrations of 2.5-10.0 mg/ml, and at a cell density of 1 X 10(6) mononuclear cells/ml. In medium supplemented with 5 mg/ml HSA, it was found that lymphocyte transformation responses, release of interleukin 2 and leukocyte inhibition factor (LIF), and the one-way mixed lymphocyte reaction proceeded in a manner analogous to that in plasma-supplemented cultures. Stimulation of LIF release by C3b was seen in HSA-supplemented cultures but not in serum-free conditions or in cultures containing 12% autologous plasma. This system can thus be used to examine cell-mediated immune responses without the interference of plasma proteins other than HSA.