Secretory lysosomes are lysosomes which are capable of undergoing regulated secretion in response to external stimuli. Many cells of the immune system use secretory lysosomes to release proteins involved in their specialised effector mechanisms. Precisely how lysosomal secretion is regulated in each of these cell types is now the study of much research as these mechanisms control the ability of each of these cells to function. Studies on a number of human genetic diseases have identified some key proteins in controlling secretory lysosome release, and now many interacting partners have been identified. The different regulatory components seem to vary from one cell type to another, providing a multitude of ways for fine tuning the release of secretory lysosomes.