CD4 and breast cancer: To determine the impact of irradiation on the tumor immune infiltrate in Brca1co/coMMTV-Cre mammary tumors, we isolated single cell suspensions from tumor tissues and conducted flow cytometry analysis of CD45+ leukocytes stained for CD11b, Gr 1, F4/80, CD4, CD8α, and PD-1 (Fig. 5A).