Sphingosine 1-phosphate (SIP) has recently been described to induce antimycobacterial activity. The present study analyses the role played by SIP in antigen presentation of monocytes and in the next activation of Mycobacterium tuberculosis (MTB)-specific CD4+ T cell response. Results reported herein show that SIP stimulation of MTB-infected monocytes (i) inhibits intracellular mycobacterial growth, (ii) enhances phagolysosorne maturation and the transit of mycobacteria in MHC class II compartments, (iii) increases the frequency of MTB-specific CD4+CD69+ T cells, expressing the inflammatory homing receptor CCR5, derived from tuberculosis patients and PPD+, BCG naive. healthy Subjects, and (iv) induces IFN-gamma production in CD4+CD69+CCR5+ T cells derived from PPD+ healthy individuals, only. Altogether, these results show that S I P promotes antigen processing and presentation in monocytes, increases the frequency of MTB-specific CD4+ T cells and can regulate IFN-gamma production by antigen specific CD4+ T cells in the course of active disease. (c) 2007 Elsevier Inc. All rights reserved.