Secretory lysosomes - A special mechanism of regulated secretion in haemopoietic cells

The secretory, granules of cells derived from the haemopoietic lineage are 'secretory lysosomes' containing both lysosomal hydrolases and secretory protein. Studies on cytotoxic T lymphocytes (CTLs) have elucidated several of the mechanisms that regulate protein sorting to, and secretion from, this unusual secretory, organelle. In particular, recent findings from a CTL mutant have led to the hypothesis that CTLs, and other cells of the haemopoietic lineage, use specialized sorting and secretory mechanisms in which the lysosome functions as a regulated secretory granule.