<p>Biosensors are advanced analytical tools that convert biological responses into measurable electrical signals, with significant applications in immune cell analysis. This review discusses the evolution, mechanisms, and classifications of biosensors, focussing primarily on their role in detecting immune markers and cellular activities. Key categories include electrochemical, optical, and mechanical biosensors, each utilizing distinct transduction methods to monitor immune cell behaviour. The review highlights the development of electrochemical biosensors for the detection of cytokines such as TNF-α and the monitoring of T-cell activation, showcasing their potential for real-time diagnostics in various medical fields including cancer immunotherapy, infectious disease diagnosis, and autoimmune disorder management. It also addresses the challenges and future directions in biosensor technology, emphasizing the integration of nanotechnology and artificial intelligence to enhance sensitivity and functionality. The prospects of wearable devices and point-of-care systems are discussed, suggesting a transformative impact on clinical practices for monitoring immune responses. Overall, the review underscores the versatility and efficacy of biosensors as indispensable tools for advancing our understanding of immune cell dynamics and improving diagnostic capabilities.</p> Graphical Abstract <p></p>