Immunoperoxidase staining of Legionella pneumophila

Immmunoperoxidase staining has been applied to sections of pneumonic lung from a previously published case of Legionnaires' disease. Specific staining of Legionella pneumophila was accomplished with sub-group 1 antiserum, which also revealed staining of phagosomes, and in some areas diffuse background staining of 'soluble' antigen. Some organisms remained unstained with the specific antiserum, and these were revealed by progressive haemalum staining. In other sections, some organisms stained specifically with rabbit anti-μ chain serum but not with anti-γ chain serum, this result suggesting that the organisms were coated with patient's IgM specific antibody.