Fig. 3.

Effects of PRRSV infection on the thymus in piglets. A Thymus atrophy. Thymus paraffin sections showed that the thymic cortical area was significantly smaller in infected than control piglets, on the basis of H&E staining (H&E, 40×). The area ratio of the thymic cortex to thymic parenchyma and thymic cortex to thymic medulla in the infected group were significantly smaller than that in the control group. B Thymic cortical cell necrosis (H&E, 400×). Necrotic cells were observed in the thymic cortex, with clear nuclear pyknosis, in the PRRSV-infected group. C Apoptosis index, detected with TUNEL assays. The number of apoptotic cells in the thymic cortex in PRRSV-infected piglets was significantly greater than that in control piglets. D α-SMA IHC staining of the thymic cortex. α-SMA was used as an immunohistochemical blood vessel marker. The number of blood vessels in the thymic cortex in the PRRSV-infected group was significantly greater than that in control piglets. E MAC387 IHC staining of the thymic cortex. MAC387 was used as a macrophage immunohistochemical marker. The number of thymic cortical macrophages was significantly greater in PRRSV-infected than control piglets. F Number of thymic corpuscles in the thymic medulla. The number of thymic corpuscles in the thymic medulla in the PRRSV-infected group was significantly greater than that in the control group. G Interstitial width of thymic lobules. The interstitial width of thymic lobules in the PRRSV-infected group was significantly greater than that in the control group. CON: control group (n = 3). PRRSV: PRRSV-infected group (n = 11). ^*P ≤ 0.05, ^**P ≤ 0.01, ^***P ≤ 0.001, ^****P ≤ 0.0001