Aim:To investigate immunologic reactions after implantation of stainless steel (SS) alloy and titanium (Ti) alloy in a rat model. Macrophage and cytokine responses have been reported after the in vivo and in vitro application of different biomaterials. Material and Methods:Wistar albino rats after an exploration of the thoracolumbar paravertebral muscle tissue of the subjects, group I underwent a sham surgery, and groups II and III were implanted Ti alloy and SS alloy rods respectively. The CD4, CD8, CD25 (IL-2R) (lymphocyte and CD4 gate), CD4+CD8+ and CD4+CD25+Foxp3+ (Tregs), IL-4, IL-10, IL-6, IL-17A, TGF-β, TNF-α in the blood were analyzed.Results:CD4, CD25 (IL-2R), CD4+CD8+ and Tregs levels were lower in the Group III compared to the sham and Group IIs. IL-6, IL-17A, TGF-β and TNF-α levels in the G III showed a significant increase on all days in comparison with the sham and Group II. IL-4 and IL-10 levels, were lower in the Group III than those in the Group II; and a significant decrease was observed in the IL-10 level. While there was a reduction in IL-6 and IL-17A levels in the Group II as opposed to the sham group.Conclusion:As opposed to SS alloy, Ti alloy suppresses the development of inflammations by inhibiting proinflammatory response; strengthens the humoral immune system by intensifying the antibody-dependent immune response; triggers the development of immune tolerance by regulating the immune response; and activates the mechanism that prevents immune response-related damage from occurring.