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

Recruitment of lymphocytes is an important feature of the host immune respo nse against pathogens. However, the mechanisms by which lymphocytes are att racted are not yet fully understood. Recently, the cDNA of a lymphocyte-spe cific 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 ce ll 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 N K 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 lev el. After activation with IL-2 or IL-12, the expression of both Lptn and SC M-1 beta was upregulated within hours. NK-92 cells maintained in medium sup plemented with IL-2 constitutively expressed SCM-1 mRNA, However, after 24 h of IL-2 starvation and subsequent culturing at various 11,-2 concentratio ns, the expression of Lptn/SCM-1 alpha was upregulated in a dose-dependent manner, whereas the expression of SCM-1 beta remained consistently high, Th ese observations indicate that NK cells, in addition to T lymphocytes, expr ess Lptn/SCM-1 alpha and SCM-1 beta after cytokine activation. The upregula tion 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 a s inflammation.