Quantitative determination of thymic eosinophilia in swine.

Thymuses from 512 slaughtered pigs weighing about 160 Kilos, were subjected to histological examination. All thymuses displayed a focal or diffuse eosinophilia in the connective tissue septa and in the lymphoid tissue, especially in the medulla. Quantitative determination of cellular density and eosinophils was performed on 30 cases, by image analysis, and the number of eosinophils was compared to the number of Hassall's bodies. Statistical analysis demonstrated a significant difference in the number of eosinophils between cases with focal eosinophilia and those with diffuse pattern (P < 0.001). The higher quantity of eosinophils was present, the higher number of Hassall's bodies was calculated per unit area of medulla (P < 0.001). The significance of this eosinophilia is obscure. It may be related to the elimination of cellular catabolism products and this agrees with the possible phagocytic activity of Hassall's bodies. However, further investigation concerning the physiopathology of the thymus must take into consideration the presence of the eosinophils granulocytes in this organ.