The possible involvement of immune complexes in pulmonary granuloma formation in experimental hypersensitivity pneumonitis

Abstract

Hypersensitivity pneumonitis (HP) is a disease caused by inhaled organic dust. The alveolitis and granuloma are characteristic features of HP. The precise mechanism of granuloma formation is still unclear. The roles of immune complexes and primed T cell in relation to granuloma formation were studied. Local lymph node cells were obtained from C57BL/6 mice immunized by injection of ovalbumin (OA) or keyhole limpet haemocyanin (KLH) emulsified in complete Freund's adjuvant into footpads. Thereafter enriched T cells were obtained by passage through nylon wool columns. Antigens (OA, KLH) were chemically coupled to Sepharose 4B beads (OA-beads, KLH-beads). The immune complex was made by the incubation of the antigen-coupled beads and the immunized mouse serum at 37 degrees C for 2 hours. The recipient mouse irradiated by 6.5 Gy was transferred with 3 X 10(7) T cells and challenged with intratracheal instillation of 1 X 10(4) antigen-coupled beads or 1 X 10(4) immune complex-coupled beads. The recipient mice were sacrificed day 3 after cell transfer and challenge. The radius of pulmonary granuloma was measured by microscopic examination of the HE-stained section. The radius of granuloma increased in the recipient mouse which received the primed T cell and was challenged with immune complex-coupled beads compared with any other combination of cell transfer and antigen challenge. This result suggests that not only T cell but also immune complexes play an important role in granuloma formation in HP.