Rosette-formation of pig thymic lymphocytes with sheep and pig erythrocytes. II. Markers for cortical and medullary thymocytes.

Study of the distribution of P+S+ and P-S+ cells in various lymphoid organs of pig revealed that the thymus contains the highest proportion of P+S+ cells (75.5 +/- 4.2%). In vivo treatment of neonatal piglets with cortisone: (i) Reduced both the area of the thymic cortex even more than the medulla and the P+S+ cells more than the P-S+ cells, suggesting the respective origin of these two populations in these two tissue compartments. Moreover, cortisone-resistant thymocytes responded better than the control untreated pig thymocytes to Con A and PHA stimulation. (ii) Reduced the number of P+S+ cells in peripheral organs. Separation of adult thymocytes into P+S+ and P-S+ cell fractions showed that P-S+ cells responded better than P+S+ to Con A and PHA stimulation. Cortisone-resistant thymocytes and P-S+ cells showed the same cell size distribution and both are enriched in medium sized cells. Thus, it is concluded that the property of rosette formation with pig red blood cells allows the identification of two subsets of pig thymocytes with different biological properties and thymic locations, which by analogy with other species may prove to have different patterns of emigration to peripheral organs.