In vitro analysis of cell-mediated immunity: clinical relevance

Cellular immunity, a major component of the immune system, contributes to protection against infections and plays a role in the rejection of foreign allografts. T helper cells and the antigen-presenting cells with which they interact provide important functions for cellular immune responses by generating helper signals via soluble molecules known as lymphokines or cytokines. As described here, in vitro analysis of markers of cellular immune function can be used for clinical diagnosis and assessment of therapeutic efficacy and to elucidate the mechanisms of immune dysregulation. Not all helper signals necessarily have the same augmenting effect, because immunoregulatory cytokines that up-regulate the cellular arm of the immune system can conversely down-regulate the humoral arm, and vice versa. The interplay between cross-regulatory cytokines determines which component of the immune system is dominant and can influence the clinical outcome of immunologically controlled diseases. Given the apparent dramatic effects of these cytokines, assays performed in future clinical laboratories should include profiles of immunoregulatory cytokines.