Using immunohistochemical studies of tissue sections and a flow cytometry evaluation of cells recovered from the bronchoalveolar lavage (BAL), we studied the role of CXCR3/CXCL10 interactions in the regulation of T-cell migration into the lung of patients with hypersensitivity pneumonitis. The gene discussed is CXCL10; the disease is hypersensitivity pneumonitis.