The Mysterious Lymphocyte

Publisher Summary This chapter gives a striking account of the history of lymphocyte. In several species, lymphocytes had been shown to enter the blood from the major lymphatic vessels in numbers sufficient to replace all those in the blood many times each day. Thus, a large number of lymphocytes numerically equal to those entering the blood, left it again for some unknown destination. The fate of these cells was the subject of much speculation. Maximov and his school regarded lymphocytes as haemopoietic stem cells capable of developing into all forms of circulating blood cells and into fibroblasts. This was the dominant view in 1953 and was based entirely on identifying the alleged transformations in histological preparations. A minor school regarded them as short-lived end cells, dying after performing their unknown function, possibly in the gut or the skin. The demonstration in 1957 that the lymphocytes that entered the blood were responsible for maintaining their output from the thoracic duct was most simply explained by a continuous recirculation of cells from blood to lymph. The next step was to see if the animals' own lymphocytes could, in fact, migrate from the blood into the lymph. The experiments on the response to alloantigen and some preliminary studies with Douglas McGregor on the possible role of lymphocytes in antibody formation led to propose in 1962 a more general function for small lymphocytes that also incorporated the phenomenon of recirculation.