Immunochemical analysis of serum-related proteins in the respiratory tract secretions of normal mice.

Normal mouse lung lavage fluid was analyzed for its content of serum-related proteins by the methods of gel filtration, immunoelectrophoresis, and double immunodiffusion. Lavage samples were collected from exsanguinated mice using three repeated infusions of 0.9% sodium chloride solution. Cells were removed, and the lavage fluid was concentrated. Approximately 0.23 mg of protein per mouse was present in the concentrated solution. Albumin, transferrin, and immunoglobulin G (IgG) were among the proteins in greatest concentration. Albumin, IgG1, IgG2, IgA, and IgM were quantitated by single radial diffusion. Although immunoglobulins could be synthesized locally, albumin and transferrin were assumed to come from plasma. The albumin content was used to estimate the amount of transudated plasma as 0.0027 ml per mouse. The IgA levels were low with an IgA/IgG1 ratio of 0.58 and an IgA/IgG2 ratio of 0.43. IgM was not detected. Goat anti-lung lavage serum revealed the presence of additional lung-related proteins.