CXCL12 and CXCL13 are two well-documented B cell chemoattractants (20, 21), and detection of CXCL12 and CXCL13 levels in BALF after viral infection revealed that CXCL13 expression at 3-5 d.p.i. The gene discussed is CXCL13; the disease is viral infectious disease.