Expression of SCM-1α/lymphotactin and SCM-1β in natural killer cells is upregulated by IL-2 and IL-12

Recruitment of lymphocytes is an important feature of the host immune response against pathogens. However, the mechanisms by which lymphocytes are attracted are not yet fully understood. Recently, the cDNA of a lymphocyte-specific chemokine, lymphotactin (Lptn), was isolated from murine and human T cells and was also found to be expressed in murine NK cells and human NK cell clones. This study investigated the influence of interleukin (IL)-2 and IL-12 on the expression of Lptn, also known as SCM (single cysteine motif)-1 alpha, and SCM-1 beta, a 97% homolog of Lptn, in freshly isolated human NK cells and the human NK cell line NK-92, Northern blot analysis and RT-PCR confirmed that nonactivated human NK cells expressed both genes at low level. After activation with IL-2 or IL-12, the expression of both Lptn and SCM-1 beta was upregulated within hours. NK-92 cells maintained in medium supplemented with IL-2 constitutively expressed SCM-1 mRNA, However, after 24 h of IL-2 starvation and subsequent culturing at various 11,-2 concentrations, the expression of Lptn/SCM-1 alpha was upregulated in a dose-dependent manner, whereas the expression of SCM-1 beta remained consistently high, These observations indicate that NK cells, in addition to T lymphocytes, express Lptn/SCM-1 alpha and SCM-1 beta after cytokine activation. The upregulation of these chemokines in NK cells on activation likely acts to increase the number of effector cells reaching the site of an immune response such as inflammation.