The THP-1 cell line is a widely used human monocytic cell line derived from an acute monocytic leukemia patient. It is commonly used in research to study monocyte/macrophage biology, immune responses, inflammation, and infection. THP-1 cells can be differentiated into macrophage-like cells using phorbol esters, allowing researchers to study the functions and responses of mature macrophages. The THP-1 cell line is valuable for studying various diseases, drug screening, and understanding the mechanisms of innate immune responses.