cellinfiltration

Cellinfiltration is a biological process in which cells move from their native compartment into surrounding tissue or across tissue barriers. The term is used broadly to describe contexts in which cells invade, permeate, or accumulate within tissues, including immune cell infiltration into sites of infection or inflammation, infiltration of cancer cells into adjacent stroma or vasculature (often described as invasion or metastasis in cancer biology), and host or donor cell infiltration during tissue grafting or transplantation. In many cases, infiltration is a tightly regulated process that serves protective or homeostatic roles, but excessive or misdirected infiltration can contribute to pathology.

Mechanisms involve chemotactic signaling that guides cells toward higher concentrations of cytokines or chemokines, adhesion to vascular endothelium and extracellular matrix via integrins and selectins, and transmigration (diapedesis) through vessel walls. Once in tissue, cells migrate using cytoskeletal remodeling and proteolytic enzymes such as matrix metalloproteinases to navigate the extracellular matrix. The exact sequence varies by cell type and context, from immune surveillance to cancer cell dissemination.

Clinical and research relevance: In inflammation and infection, infiltration of neutrophils, macrophages, lymphocytes helps clear pathogens but can cause tissue damage if prolonged. In cancer, infiltration by lymphocytes (tumor-infiltrating lymphocytes) or other immune or stromal cells influences prognosis and response to therapy. In transplantation, infiltration can reflect rejection or tolerance. Methods to study infiltration include histology and immunohistochemistry, flow cytometry, and in vivo imaging.