CD4 and pulmonary fibrosis: Further, untreated Radpf1 mice, which are spared radiation-induced lung fibrosis and which have C3H/HeJ alleles on chromosome 17, were shown to have pulmonary CD4 lymphocyte % as in C3H/HeJ mice, supporting the pre-treatment association of pulmonary CD4 with the trait of radiation induced pulmonary fibrosis in this mouse model.