Systemic immune cells

Systemic immune cells represent the collective population of white blood cells, or leukocytes, that circulate through the cardiovascular and lymphatic systems to provide host defense and maintain tissue homeostasis [1][2]. This heterogeneous group includes lymphocytes (T cells, B cells, and natural killer cells), monocytes, and granulocytes, each playing specialized roles in innate and adaptive immunity [1][4]. In therapeutic development, these cells are often the primary focus for modulation; for instance, checkpoint inhibitors activate systemic T cells to combat malignancy, while immunosuppressive agents dampen their activity to treat autoimmune diseases or prevent organ transplant rejection [3][4]. However, because the term refers to a broad cellular compartment rather than a specific protein, enzyme, or receptor, it is classified as a biological system rather than a discrete molecular target [3]. Monitoring the composition and activation state of these cells is critical for assessing therapeutic efficacy and managing risks such as cytokine release syndrome or systemic immunosuppression [4].

Other names

Peripheral blood mononuclear cells (PBMCs)Circulating leukocytesWhite blood cellsSystemic immunity

Drugs targeting systemic immune cells act by modulating intracellular signaling pathways, depleting specific cell populations via antibody-dependent cellular cytotoxicity, or blocking inhibitory checkpoint receptors to restore or suppress immune activity [3][4].