The kinetics of thymocytes apoptosis at different days post-infection (dpi).

<p>The percentages of apoptotic cells in the thymus of one representative HuN4-infected piglet at 7 (A) and 10 (C) dpi, and apoptotic cells in the thymus of a representative age-matched control piglet at 7 (B) and 10 (D) dpi. Apoptotic cells were quantified by flow cytometry using FITC-labeled Annexin V. Q1, necrotic or another cell population that was FITC-Annexin V-negative and PI-positive; Q2, end stage apoptotic or a dead cell population that was FITC-Annexin V- and PI-positive; Q3, a viable cell population that was not undergoing apoptosis and was both FITC-Annexin-V- and PI-negative; Q4, an early apoptotic cell population that was FITC-Annexin V-positive and PI-negative.