Stages in Dendritic Cell - Initiated

Previous studies of dendri t ic cells (DC)1 (reviewed in 1-3) have revealed the potent immunos t imu la to ry capacities of this class of leukocyte. However, relatively little is known of their mechanism of action. We have used a polyclonal lymphocyte mitogenesis system to examine this question. Kl inker t et al. (4) and Phillips et al. (5) showed that T cells, modified with sodium periodate, proliferate quickly and extensively in the presence of DC. This assay has been used to identify two stages in oxidative mitogenesis. In the first stage, viable DC induce both the release of T cell growth factor, or in ter leukm 2 (IL-2) (reviewed in 6-8), and T lymphocyte responsiveness to IL-2. In the second stage, which can occur in the absence of DC, IL-2 alone mediates proliferat ion of these responsive T cells.