Effect of thymectomy on lymphocyte subpopulations in the pig. Demonstration of a thymus-dependent 'null' cell.

Thymectomy in neonatal pigs results in marked lymphopenia. Surface Ig immunofluorescence, Fc rosettes and SRBC rosettes have been used to identify blood lymphocyte subpopulations. There was no marked reduction in numbers of cells in these subpopulations after thymectomy, although their proportion increased. This change was explained by a 90% reduction in 'null' lymphocytes, defined as those lacking sIg and Dextran SRBC receptor, which comprised 30-45% of blood lymphocytes.