CXCL1 and infection: Having demonstrated deficient neutrophil recruitment in the ECRG4 KO infection despite intact local proinflammatory mediator production, we next used qPCR to evaluate the expression of genes that regulate neutrophil responses to the cytokine IL-1β and chemokines CXCL1 and CXCL2, as these are critical to early neutrophil recruitment and abscess formation in MRSA infection [25, 26].