BACKGROUND In the current study we focused on changes in the immune parameters of patients with CF after lung transplantation (Tx), with particular emphasis on the interaction of the immune system, infection, the autoimmune phenomenon observed in some CF patients, and immunosuppression. MATERIAL AND METHODS Seven transplant patients with CF were investigated, 3 men and 4 women; the average age at Tx was 24.2 years (20.2-32.3). The parameters of both humoral immunity (immunoglobulins, complement, CRP, antinuclear and antineutrophil cytoplasmic antibodies) and cellular immunity (T and B lymphocytes, NK cells) were traced. RESULTS We observed marked initial hyperimmunoglobulinemia, with a sharp drop in immunoglobulin levels within 1 month after Tx. Positivity for antineutrophil cytoplasmic antibodies (ANCA) was found in 3 patients before Tx. A strong ANCA positivity persisted 2 months after Tx despite deep introductory immunosuppression. In one patient ANCA positivity, after a transient negative result at months 2 and 12 after Tx, reappeared one year after Tx. The Burkholderia cepacia infections found in 2 patients proved to be lethal. CONCLUSIONS In our series of CF lung transplant recipients, we found Burkholderia cepacia infection to be a risk factor. The robust appearance of autoantibodies and their persistent positivity for many months despite deep immunosuppression is a remarkable feature observed in some CF patients.