CD4 and lung carcinoma: The immune function in lung tissues of the three groups of rats showed that CD3+, CD4+, CD4+/CD8+ of normally fed rats were higher, and CD8+ was declined compared with that of lung carcinoma model rats; and CD3+, CD4+, CD4+/CD8+ of IDO inhibitor rats were higher, and CD8+ was declined compared with that of lung carcinoma model rats.