Multiple chemotactic factors: fine control or redundancy?

Recruitment of leukocytes either during development or to the site of injur y is crucial. The molecular regulation of cell trafficking is complex but w ell orchestrated by the temporal and spatial expression of a multitude of c hemokines (chemoattractant cytokines) and chemokine receptors. The chemokin es, classified primarily into four classes (CC, C, CXC and CX,C) bind eithe r to specific or shared receptors and often exhibit intra-class redundancy. At the cellular level, the biological activity of chemokines is finely con trolled by varied receptor display, binding affinity and/or varied signal-t ransducing mechanisms. Perturbation in these finely regulated processes lea ds to acute or chronic inflammatory conditions, developmental abnormalities and tumorigenesis/angiogenesis.