The discovery of new adjuvants that can stimulate the immune response to protein antigens is a major issue for the development of subunit vaccines. Lipoprotein oxidation occurring during the acute phase response (APR) to aggression of the organism, provides signals of danger that are detected by dendritic cells (DC). Among other instructive molecules generated during the APR, lysophosphatidylcholine (LPC) promotes mature DC generation from differentiating human monocytes in vitro. It is shown here that LPC also controls the initiation of an adaptive immune response in vivo. LPC displays adjuvant properties when injected to mice in mixture with various antigens. Immunizations with LPC induced the production of antigen-specific antibodies with an efficiency similar to Alum, the reference adjuvant for human vaccination. Importantly, LPC also induced cytotoxic T cell responses, opening perspectives for vaccine development. Therefore, LPC is a natural adjuvant for the immune system, inducing humoral and cellular immune responses.