Effects of NiO inhalation on alveolar macrophages and the humoral immune systems of rats

To study the effects of inhaled NiO particles on alveolar macrophages and the humoral immune system, male Wistar rats were continuously exposed to NiO aerosols for 4 weeks and 4 months, respectively. Fractions of alveolar macrophages, granulocytes, and lymphocytes in lung lavages, number of polynucleated macrophages, size of macrophages, and phagocytic activity were determined. To test the effects on the humoral immune response sheep erythrocytes were injected, and the antiserum titer in blood and the portion of antibody forming cells in spleen were measured. Significant alterations were found in both systems at 100 and 200 µg Ni/m3 after 4 weeks of exposure and at 25 and 150 µg Ni/m3 after 4 months of exposure, respectively. The results demonstrate the usefulness of investigations on the humoral immune system and alveolar macrophages as sensitive parameters in detecting effects of NiO inhalation.