Background: Brucella is a well-known intracellular bacterium entailing acute and chronic illnesses in humans and domestic animals. The infection chronicity may be affected by the cell-mediated immunity and cytokine patterns. Objective: To evaluate the patterns of T-helper cytokines in patients suffering from chronic and acute brucellosis. Methods: In this cross-sectional study, 22 individuals with acute brucellosis, 21 individuals with chronic brucellosis, and 21 healthy individuals with the same genetic background were recruited from October 2015 to April 2016. Peripheral lymphocytes were isolated and stimulated by phytohemagglutinin (PHA) and brucella antigen in cell culture. The lymphocyte proliferation was detected by MTT assay. After collecting the supernatants, and through the use of ELISA method, we quantified the interferon gamma (IFN-γ), interleukin (IL)-5, IL-17 and transforming growth factor–beta (TGF-β). Results: Patients with chronic brucellosis had a lower level antigen-specific stimulation index compared to those suffering from acute brucellosis (p=0.0001). Cases with chronic brucellosis had a lower level of IFN-γ compared to cases with acute brucellosis (p=0.001). Finally, patients with chronic brucellosis had higher levels of IL-5 and TGF-β in comparison with the acute group (p=0.01 and p=0.04, respectively).Conclusion: Chronic brucellosis reduces lymphocyte proliferation and TH1 cytokine secretion, but it enhances IL- 5 and TGF-β production. Polarizing the immune responses plays a crucial part in the progression and development of chronic diseases.