The CD28 gene, located on chromosome 2q33, encodes a protein that is a key co-stimulatory molecule in T-cell activation. CD28 is expressed on the surface of T-cells and interacts with B7 molecules (CD80 and CD86) on antigen-presenting cells (APCs). This interaction is essential for the full activation of T-cells, leading to their proliferation, cytokine production, and differentiation into effector and memory cells. Without this co-stimulation, T-cells can become anergic or undergo apoptosis.The importance of CD28 in immune responses is well-documented. It plays a crucial role in maintaining the balance between immune activation and tolerance. Dysregulation of CD28 signaling has been linked to various autoimmune and inflammatory diseases, such as rheumatoid arthritis and multiple sclerosis. Additionally, CD28 is a target for immunotherapy, particularly in the context of cancer treatment. Chimeric antigen receptor (CAR) T-cells, which are engineered to express CD28 as part of their co-stimulatory domain, have shown significant promise in treating hematological malignancies.