from Scandinavian Joumal of Immunology 2002 - July ; 56 ( 1 ) : 1 - 11 25

doi: 10.1111/j.1365-3083.2006.01767.x Ghost Lab, l.aboratorv of Cellular and Molecular Immunology, Natienat lnstitute of Alterqv and lnfectious Diseases, National lnstitutes ofHealth, Bethesda, MD, USA Received 22 Morch 2006; Accepted in revisedterm 8 April 2006 Com-spcncence la: DI' K. Abdi, Ghost Lab, l.aboratorv of Cellular and Molecular Immunology, National lnstitute of Allergy and Infectious Discases. National lnstitutes of Health, 9000 Rockville Pike, Buiiding 4, Room 111 msc-0420, Bethesda, MD 20892-0420, USA. E-mail: [email protected] is currently thought rhat IL-12, produced by dendritic cells (DC) early aftel'stirnulation by bacterial pathogens or lipopolysaccharide (LPS), acts as a pro-inflammatory cytokine bridging rhe innare and adaptive immune responses. \1Vefound, however, that ir is only the p40 subunit and not the IL-12p/5 hetero-dimer that is sectered early in copieus amounrs in response to LPS. Ncithernaïve T cells, nor a variery of microbial producrs, were abIe to induce IL-12p/5production unle ss the De were conditioned by the presence of inrerferon-y(IFN.·'() or by encounter wirh previously activared T cclls. Thc inabiliry of naïveT cclls or of bactcrial produces ro induce IL-12 argues against irs carly role as theinitiator of innare and adaptive immune responses.