OBJECTIVES: Pulmonary involvement of varying etiology is common in collagen vascular diseases (CVDs). Bronchoalveolar lavage fluid (BALF) cell differentials reveal information on the immune mechanisms involved in the CVDs. The aim of the present study was to evaluate BALF cell populations in CVD-associated ILD and to investigate possible correlation with pulmonary function.METHODS: Fifty-seven patients (26 male and 31 female, mean age ± SD: 54.68±12.18 years) with CVD-associated interstitial lung disease were studied. Patients were divided into 6 groups based on underlying CVD. The study population also included a group of 10 healthy controls. BALF was examined in all individuals. Cell density, total cell number and differential cell count were recorded. BALF lymphocyte subsets were analysed by dual flow cytometry. Pulmonary function was assessed in all patients.RESULTS: BALF differential cell count did not differ significantly among the different groups. Scleroderma patients showed the highest percentage of CD19 cells (p<0.001). The NK and NKT cell percentages were significantly higher in systemic lupus erythematosus and in Sjögren, respectively, compared to other CVDs and controls (p=0.001 and p<0.001). Also BALF neutrophil percentage correlated negatively with FVC (r=-0.356, p=0.011) and FEV1 (r=-0.336, p=0.017) and BALF NKT cell percentage correlated negatively with pO2 (r=-0.415, p=0.003).CONCLUSIONS: Important variations observed in BALF cell populations suggest the implication of NK and NKT cells in the pathogenesis of lung involvement in CVDs.