Figure 2. Recruitment of neutrophils into the joint in immune complex-induced arthritis is mediated by a temporal cascade of chemoattractants.

(1) At early time points, LTB₄ is required to recruit and activate a small number of neutrophils. (2) These recruited neutrophils release IL-1β in the joint, which induces the release of predominantly CCR1 ligands at first and later CXCR2 ligands from cells in the joint. (3) CCR1 ligands are required to recruit the next wave of neutrophils into the joint, and this recruitment of neutrophils is broadly amplified in the last step of the cascade when (4) CXCR2 ligands released form neutrophils themselves potently recruit large numbers of neutrophils into the joint.