To evaluate the effects of a monoclonal antibody against interleukin-8 (K2.2) on the microvascular fluid flux after combined injury by burn and smoke inhalation. Fourteen sheep were prepared surgically by placing a lung lymph catheter and a flank lymph catheter to examine the microvascular fluid flux. After a recovery period, they were subjected to a combined injury of 40% third-degree burns on the flank and smoke inhalation. This combined injury induced a rapid increase in burned tissue lymph flow (b-Q(L)) and a delayed-onset increase in lung lymph flow (l-Q(L)). The initial increase in b-Q(L) was associated with an elevation of the lymph-to-plasma oncotic pressure ratio, which led to a predominant increase in the burned tissue permeability index (b-PI). Pretreatment with K2.2 had no effect on the permeability change seen in the burned tissue; however, the lung permeability changes were attenuated by pretreatment with K2.2. These findings indicate that the pathogenesis of the increase in microvascular fluid flux seen after the combined injury differs in burned tissue and the lung.