Immunzellinfiltration

Immunzellinfiltration, or the infiltration of immune cells into tissues, is a key feature of many normal and diseased states. It describes the presence and distribution of immune cells within the parenchyma or stroma of organs, often in response to infection, injury, autoimmune activity, or neoplastic growth. The extent and pattern of infiltration can influence tissue function and disease progression.

The infiltrating cells are primarily lymphocytes (such as CD8+ cytotoxic T cells and CD4+ helper T cells, B cells), macrophages, neutrophils, dendritic cells, and natural killer cells. Recruitment is driven by chemokines and cytokines released by resident tissue cells or invading pathogens. Circulating leukocytes reach the tissue by rolling, adhesion, and transmigration across the endothelium, mediated by selectins, integrins, and adhesion molecules, followed by migration along chemotactic gradients.

Infections typically show targeted infiltration aimed at eliminating pathogens. Autoimmune and chronic inflammatory disorders involve sustained infiltration that can damage tissue. In cancer, tumor-infiltrating immune cells constitute a critical aspect of the tumor microenvironment. The composition and activation state of infiltrates (for example, cytotoxic CD8+ T cells versus regulatory T cells or tumor-associated macrophages) can be associated with prognosis and response to treatments, including immunotherapies.

Assessment is based on histology and immunohistochemistry to identify cell types and density. Common markers include CD3 for T cells, CD20 for B cells, CD68 for macrophages, and CD56 for NK cells. Clinically, patterns of immunzellinfiltration inform diagnosis, prognosis, and therapeutic planning in several diseases, particularly oncology.