Figure 9.

Model for the role of CXCR2 in antibody-mediated immunity to pneumonic plague. Antibody-opsonized bacteria are expected to be taken up by macrophages and neutrophils via the FcγR, and although this may not lead to bacterial clearance by either cell type, chemokines may still be secreted. Simultaneously, activation of C5a convertase leads to increased C5a, which also acts as a chemoattractant for neutrophils and other cells that express the C5a receptor (C5aR). C5aR and CC receptors would be expected to promote neutrophil chemotaxis but may be prevented from activation because of Yersinia virulence factors encoded within the pgm locus. In contrast, CXC chemokine signaling may be required to activate effector functions independent of neutrophil chemotaxis, such as increased intracellular Ca²⁺, stimulation of granuole release, or secretion of neutrophil extracellular traps (NETs) that promote bacterial clearance, and protect the host from disease.