CYSTIC fibrosis provides an opportunity to study the immunoglobulin response of children, adolescents, and young adults who have chronic pulmonary bacterial infection, yet who seem to be resistant to secondary acute bacterial complications such as septicemia and meningitis. Until recently, three main classes of human serum immunoglobulins have been recognized: IgG (Immunoglobulin G, γG, or 7S γ2-globulin), IgA (Immunoglobulin-A, γ A, γ1A, or β2A-globulin), IgM (Immunoglobulin-M, γM, γ1M, β2M, or 19S γ1-macroglobulin). Antibody activity has been associated with each of these classes. A fourth class, IgD (Immunoglobulin-D), has been added to this list;1 however, its function has yet to be elucidated. Although hypergammaglobulinemia has been well described in cystic fibrosis,2 quantitative documentation of the immunoglobulin classes affected has not been recorded. The present study was undertaken to determine which immunoglobulin classes are involved in the serologic response to chronic pulmonary infection in cystic fibrosis.
Since IgA is the