Cystic fibrosis is an autosomal recessive disease with known mutated genes and a range of clinical problems which are dominated besides other clinical conditions by the chronic inflammation of the lungs. The immune system plays a major role in the defense against chronic and usually lifetime infection with strains of the Pseudomonas species, which represent the major pathogenic problem in patients with cystic fibrosis. In the current study we followed the development of immunoglobulin isotypes in patients with CF during childhood. We found mild hypogammaglobulinaemia in the earliest period of life, between the first and the third year, followed later by typical hyperimmunoglobulinemia characteristic for cystic fibrosis. Hypogammaglobulinaemia was mainly due to the low levels of IgG2. As IgG2 plays a major role in the defense against Pseudomonas we suggest that this decrease of IgG2 may predispose children to the chronic infection later in their lives. The study opens the possibility to substitute the patients with immunoglobulins in these critical periods. Besides these developmental changes in humoral immunity we frequently observe positivity of antineutrophil cytoplasmic antibodies in children with cystic fibrosis. These antibodies do not follow any age related changes and can have a complex influence on the immune response in cystic fibrosis patients.

        Key words: cystic fibrosis, immunoglobulins, IgG, IgG2, autoantibodies, ANCA