The proportion of CD161+ Vδ1+ γδ T cells in PBMCs correlated negatively with serum KL-6 values (indicative of active interstitial lung disease) among IP+ SSc patients, whereas that of total Vδ1+ γδ T cells and CD161-Vδ1+ γδ T cells did not. The gene discussed is KLRB1; the disease is interstitial lung disease.