Fig. 3.

Schematic summary of the construction of health-promoting living conditions using negatively charged particle-dominant indoor air conditions. IL interleukin, NK: natural killer. a Mechanisms yielding negatively charged particles dominant indoor air condition (NCPDIAC), b slight but significant elevation of IL-2 by short term (2.5 h stay in CPDIAC), c activation of NK cell killing activity by medium stay (2-week night stay in NCPDIAC), d slight but significant activation of T cell and NK cells examined in vitro experiments resembling NCPDIAC situation, e setting of Sumicas^® to produce NCPDIAC at living or sleeping rooms in actual resident homes and experimental trials of 3 months ON or OFF, and f elevation of NK activity in 3 months ON trials and reduction of it in 3 months OFF trials