Classification of newly formed and migrating splenic lymphocytes.

Newly formed lymphoid cells in the spleens of normal young pigs were selectively labelled with 3H-TdR, using an extracorporeal perfusion system. One day later splenic and blood lymphocytes were separated by rosetting with sheep red blood cells for classical T cells and by a direct anti-globulin rosetting reaction for B cells. The proportion of newly formed lymphocytes in these subsets was determined by autoradiography. In this study we show that while both B and T lymphocytes are produced, B cells show a much higher incidence of newly formed cells. Labelled populations of spleen derived T and B lymphocytes were also found in the blood, but the B cells showed a lower labelling incidence than in the spleen.