Microfluidic Strategies for Immune Cell Enumeration and Functional Analysis Directly from Whole Blood.

The enumeration and functional analysis of immune cells in whole blood are foundational pillars for disease diagnosis and medical innovation; however, conventional techniques requiring extensive sample preparation often suffer from sample loss, contamination, and phenotypic alterations. Microfluidic technology has emerged as a transformative solution to address these challenges, offering precise spatiotemporal control over cellular microenvironments and enabling integrated analysis directly from whole blood to maximally preserve native cellular states. In this review, we summarize recent advances in microfluidic strategies for whole-blood immune cell profiling. We first systematically introduce the principles and representative platforms for immune cell enumeration, covering both electrical impedance and optical-based methods. We then examine emerging strategies for characterizing key immune functional behaviors, including cell migration, rolling dynamics, neutrophil extracellular trap (NET) formation, and cell activation, while highlighting the potential of these platforms for integrated "sample-to-answer" analysis. Finally, we discuss the current challenges impeding clinical translation and envision future perspectives.