Flow Cytometric Analysis of Leukocytes in Porcine Mammary Secretions

Nine sows were monitored for leukocyte subsets in mammary secretions during lactation. Using flow cytometry, percentages of monocytes/macrophages (CD45CD14), T cells (CD3), and their subpopulations (CD4, CD8 and double positive (DP) CD4CD8), and B cells (CD21) in colostrum and milk were determined. The mean percentage of CD3cells was relatively stable throughout lactation. About 40% of colostral lymphocytes were identified as CD3, while in milk they comprised from 24% to 39%. The percentage of both CD8 and CD4 cells were relatively stable during lactation, beside significant decrease at the last day of lactation. Double positive cells comprised a small percentage of cells and did not exceed 7.5%. The frequency of DP lymphocytes increased significantly 6 h after parturition, and then remained relatively stable until 20 d of lactation, followed by a significant decrease at day 28 postpartum. The CD8 cells prevailed over CD4 cells throughout whole lactation. The CD4/CD8 ratio was similar during lactation period and ranged from 0.50 to 0.53 at the beginning and the end of lactation, respectively. Lymphocytes B represented about 20% of all lymphocytes of mammary secretions. CD45CD14 cells ranged between 5.01 and 10.14 % of all leukocytes.