We further examined the gene expression of pro-inflammatory chemokines (CXCL1, CXCL2 and CCL2), chemokine receptor CCR7, and TLR4 in lung tissues in order to determine the potential mechanism(s) of immune cells infiltration into the lungs of newborns following low dose infection with B. pertussis. The gene discussed is CXCL2; the disease is infection.