This is an example of a membrane potential assay where neutrophils were loaded with a cyanine probe and stimulated with PMA (left)or fMLP (right). Interestingly on the right, the cells were also 24 hours old and it is apparent that while normally when activated by fMLP, nearly all the neutrophils will repolarize within a few minutes. However, because these cells are 24 hours old, they fail to repolarize indicating a loss of functional integrity. This is despite the fact that these cells appear to produce normal amounts of respiratory burst and also appear to phagocytose normally. Clearly, the membrane potential is one of the earlier functions to suffer from “old age”!!
