Ceil to cell interaction in the immune response. II. The source of hemolysin-forming ceils in irradiated mice given bonemarrow and thymus or thoracic duct lymphocytes, or
- G. F. Mitchell, J.F.A.P. Miller
- Exptl. Med
Neonatal thymectomy depresses the immune response of conventional and germfree mice to sheep erythrocytes (1, 2). The capacity to produce 19S hemolysin-forming cells develops later after thymectomy at birth and the number attained at the height of the response is approximately 1 logt0 lower than in normal mice (1, 3). Thoracic duct cell output studies indicate that the number of recirculating small lymphocytes may be as low as 1% of normal (3). In addition, the thoracic duct cell population of neonatally thymectomized mice is markedly deficient in cells capable of transferring adoptively, to heavily irradiated mice, immunological responsiveness to sheep erythrocytes (3). Studies with tritiated thymidine-labeUng techniques (4, 5) indicate that some lymphocytes may leave the thymus and eventually appear in those areas of the lymph nodes and spleen known to be the site of traffic of recirculating small lymphocytes (6). The evidence obtained from the labeling and thymectomy experiments support the concept that the thymus may be the original source of some of these recirculating cells (7). Further support for this would be obtained if it could be shown that, under certain experimental conditions, thymus lymphocytes behaved and functioned exactly as thoracic duct lymphocytes.