HIV-1 Tat inhibits the activation of CAMKII in NK cells, providing evidence that Tat inhibits NK cell activation which might contribute to the impairment of natural immunity in HIV-1 infection. Tat-induced IL-10 expression is regulated by p38 MAPK- and CaMK II-activated CREB-1 as well as Sp-1 transcription factors. The gene discussed is SP1; the disease is HIV-1 infection.