Kinetics of immunoglobulin transport into canine bronchial secretions.

Radiolabeled 125I Preparations of canine IgG, IgM, and F(ab')2 fragments of IgG were injected intramuscularly into normal dogs to quantitate the transfer of immunoglobulins from the intravascular space into the lower respiratory tract and to observe the clearance of these proteins from lung secretions. Respiratory fluids were sampled by serial broncho-alveolar lavages during a 3-4 week interval. Only a small portion (0.15%) of the passively administered IgG was recovered in respiratory specimens indicating that minimal transfer of humoral IgG occurs under normal conditions. Alteration of the IgG molecule by removal of the Fc portion almost eliminates its penetration into lung secretions. Furthermore, IgM, which is not a prominent component of normal lung secretions, is not detected in these secretions following passive intramuscular injection.