Responses of Human Large Granular Lymphocytes and Classical T-Cells in Culture to Allogeneic Cells, Lectins, and Soluble Antigen

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Abstract
Subpopulations of human peripheral blood mononuclear lymphocytes, after depletion of B-cells and monocytes (by sequential adherence to plastic and nylon wool columns) were separated by Percoll density gradient centrifugation and tested for their ability to proliferate in response to various mitogens, recall antigens, and alloantigens, and to develop cytolytic reactivity in vitro. The low-density fraction [mostly large-granular lymphocytes (LGL)] contained greater than 95% of the total cytotoxic activity of unfractionated nonadherent lymphocytes, against the natural killer (NK)-susceptible K562 target cell, and against other NK-susceptible targets, whereas the high-density lymphocyte fraction (mostly classical T-lymphocytes) demonstrated little or no cytolytic activity against these targets. Conversely, cytotoxic alloreactivity against the lymphoblasts of the donor used for stimulation developed only in the cultures of high density cells. Autologous cytotoxic reactivity, against autologous phytohemagglutinin (PHA)-stimulated lymphoblasts, was not restricted to either subset but developed by both LGL as well as high-density lymphocytes. LGL and high-density T-lymphocytes demonstrated significant proliferative responses to lectins [PHA, concanavalin A (Con A), pokeweed mitogen], and the responses of the LGL were similar in magnitude to those of peripheral blood mononuclear cells or of high-density T-cells. In contrast, only T-lymphocytes responded to the specific recall antigen, purified protein derivative (PPD). These results indicate that LGL are capable of proliferative responses to various lectins, but have no detectable specific memory responses to a soluble antigen. In addition, a different subset of lymphoid cells was responsible for the development of NK-like and specific alloreactivity. Therefore, NK cells and T-cells, although sharing proliferative responses to mitogens, exhibit different function regarding cytotoxic effectors.