Figure 5

Evidence for apoptosis and immune cell infiltration during postpartum breast involution. Aa, b. H & E stained sections showing lactational and involutional morphology of lobules within an actively involuting postpartum breast. Ac, d. Apoptosis is evident in lobules with involutional morphology as detected by TUNEL stain (TdT nick end labeling) (arrow). Inset shows single acini in an involutional lobule with two apoptotic epithelial cells. B. Quantitation of TUNEL staining in lactational and involutional lobules from early involution breast tissue obtained from six women (*P <0.0001). C. Quantification of CD45⁺ immune cell numbers across reproductive groups of nulliparous (N) (n = 24), pregnant (P) (n = 7), ≤1 to ≤6 (n = 9), >6 to ≤12 (n = 7) and >12 to ≤24 months (n = 6), and >2 to ≤3 (n = 10), >3 to ≤6 (n = 13), >6 to ≤10 (n = 8) and >10 years (n = 13) postpartum. When compared to nulliparous cases there is a significant increase in CD45⁺ cells during pregnancy (*P = 0.005), ≤1 to ≤6 months (**P = 0.0002) and up to >6 to ≤12 months postpartum (***P = 0.01). D. Quantification of CD68⁺ macrophages by reproductive groups including nulliparous (N) (n = 12), pregnant (P) (n = 8), and ≤6 (n = 4), >6 to ≤12 (n = 5) and >12 to ≤24 months (n = 10), and >2 to ≤3 (n = 5), >3 to ≤6 (n = 7), >6 to ≤10 (n = 7) and >10 years (n = 19) postpartum. There is a significant increase in CD68⁺ cells during pregnancy (*P = 0.01), ≤1 to ≤6 (**P = 0.0001), >6 to ≤12 (***P = 0.01) and up to 24 months postpartum (****P = 0.02) when compared to nulliparous cases. All error bars represent standard error of the mean (SEM).