ELEVATED MONOCYTE INTERLEUKIN-6 (IL-6) PRODUCTION IN IMMUNOSUPPRESSED TRAUMA PATIENTS .2. DOWN-REGULATION BY IL-4

Aberrant monocyte mediator production is pivotal in the development of posttrauma immunosuppression. We have previously shown that immunodepressed trauma patients' monocytes produce elevated interleukin-6, suggesting their in vivo preactivation. This study confirms that preactivated patients' MO produce greater levels of IL-6 than normals' MO to the same in vitro Fc-gamma-RI stimulation. We also demonstrate the capacity of interleukin-4 to downregulate the elevated interleukin-6 production of trauma patients' in vivo preactivated monocytes. Monocyte interleukin-6 downregulation by interleukin-4 is dose dependent and occurs whether Fc-gamma-RI cross-linking, muramyl dipeptide, indomethacin Plus muramyl dipeptide, or interferon-gamma plus muramyl dipeptide is the interleukin-6 inducing stimulus. Furthermore, interleukin-4-dependent downregulation of monocyte interleukin-6 expression is confirmed at both the supernatant and the mRNA levels. Simultaneous downregulation of posttrauma elevated monokines implies a possible therapeutic benefit of interleukin-4 for trauma patients,