The intriguing role of polymorphonuclear neutrophils in antitumor reactions

Polymorphonuclear neutrophils (PMNs) are the most abundant circulating blood leukocytes. They provide the first-line defense against infection and are potent effecters of inflammation. In addition, their release of soluble chemotactic factors guides the recruitment of both nonspecific and specific immune effector cells.(1) Finally, since they both respond to and produce cytokines,(2,3) they also modulate the balance between humoral and cell-mediated immunity by contributing to the promotion of a T(H)1 or T(H)2 response.(4) In these ways, PMNs are engaged in a complex cross-talk with immune and endothelial cells that bridges innate and adaptive immunity,(5) Even though many facets of their biology have been thoroughly investigated,(6) PMNs still have every reason to complain of the disdain with which they are regarded by oncologists and immunologists.(2) So widespread is T-cell chauvinism(7) that the antitumor potential of PMNs continues to receive little attention, and researchers have not yet fully considered the possibility of exploiting their functions as effective weapons against cancer.