B-lymphocyte function in cystic fibrosis.

The susceptibility of patients with cystic fibrosis to chronic, progressive bacterial pulmonary infections has not been adequately explained. We explored peripheral blood B-cell function in 21 cystic fibrosis patients and in normal controls. All patients were above 10 years of age, and chronically colonized with Pseudomonas aeruginosa. Spontaneous plaque-forming cells, which reflect B-cell differentiation into immunoglobulin-secreting cells in vivo, and plaque-forming cells formed after activation with pokeweed mitogen or staphylococci in vitro, were studied. Cystic fibrosis patients had significantly higher spontaneous plaque-forming cells than normal individuals. This difference was due to the increase of spontaneous plaque-forming cells than normal individuals. This difference was due to the increase of spontaneous plaque-forming cells in patients with less severe pulmonary disease, since patients with advanced pulmonary disease had numbers of circulating immunoglobulin-secreting cells, similar to normal individuals. Both groups of cystic-fibrosis patients have a significant impairment of B-cell differentiation in response to polyclonal activation in vitro. This functional abnormality could not be explained by the presence of increased numbers of adherent suppressor cells, or by the presence of increased suppression by T-lymphocytes. The implications of our data for the increased susceptibility to infection and for the development of antibody-mediated hypersensitivity reactions are discussed.