A Common Mucosal Immunologic System Involving the Bronchus, Breast and Bowel

The immune response of the upper respiratory tract is characterized by a predominance of secretory IgA anitbody in local secretions and IgA containing cells in the lamina propria (1). The amount of IgA which is present at various levels of the respiratory tract differs since much more IgA is found high, than low, in the respiratory tract (2). The amount of IgA relative to IgG diminishes in secretions derived from lower in the tract, so that washings derived from the alveolar spaces show a ratio of the two immunoglobulins which approximates that of serum (2).