This study we examined ex vivo potential of the immune response after stimulation of whole blood with L. pneumophila SG 1, SG 2-14 and L. pneumophila standard strain ATCC 33152 in immunocompromised patients, such as: hemodialysis patients and patients after renal transplantation. The levels of TNF-α and IFN-γ in supernatants were measured with the use of commercial ELISA kits. The synthesis of TNF-α and IFN-γ after stimulation with L. pneumophila were analyzed in two aspects: differentiated stimulatory activity in relation to SG 1, SG 2-14 and ATCC 33152 L. pneumophila and differentiated response of the hemodialysis patients and patients after renal transplantation in relation to the control group. The positive and negative results of anti-L. pneumophila antibodies of two groups of our patients were found for the analysis of the stimulatory activity of L.pneumophila as a primary or secondary response. In patients with immunosuppression the response in the secretion of cytokines (TNF-α and IFN-γ) was reduced after stimulation of L. pneumophila SG 1 but in varying degrees after stimulation of L. pneumophila SG 2-14, which indicates that the risk of the infection is varied.