Differential counts of B and T lymphocytes in the lymph nodes, circulating blood and spleen after inhalation of high concentrations of diesel exhaust

Inhalation of diluted diesel engine exhaust results in the deposition of submicron carbonaceous particles in the respiratory airways. The particles are phagocytized by the pulmonary alveolar macrophages and cleared from the respiratory tract via the mucociliary escalator or through lymphatic channels. Lung clearance via lymphatics results in accumulation of particles in the regional lymph nodes. Differential counts of B and T lymphocytes were performed to determine whether the deposited carbon particles in the lymphatic tissue can alter the subpopulation composition of various lymphoid compartments. In contrast to the effect of materials such as heavy metals, halogenated hydrocarbons or cigarette smoke condensate, all of which have been shown to alter B and T cell differential counts of lymphoid compartments under various test conditions, assays of lymphocytes from tracheobronchial lymph nodes, spleen and blood from guinea pigs exposed to diluted diesel exhaust with a particulate concentration of 1500 micrograms m-3 for up to 8 weeks revealed no significant changes when compared with age-matched controls. Furthermore, cell viability as measured by trypan blue exclusion in the exposed groups was comparable to that of the age-matched controls. These data indicate that, within the range of tested conditions, the deposited diesel particles do not exert major effects on the parameters of the immune system that were measured.