Large granular lymphocytes: morphological and functional properties. I. Results in normals

Large granular lymphocytes (LGL) represent a morphologically distinct mononuclear cell type. In healthy individuals an average of 12.5 +/- 5.2% of peripheral mononuclear cells exhibit this morphology. Structurally they are characterized by azurophilic granules, light cell density, low surface adherence and expression of Fc-IgG receptors. Functional analyses on LGL suspensions enriched by means of density gradient fractionation and adherence procedures included testing of T-cell and monocyte-specific in vitro reactions as well as evaluation of their natural cytotoxicity (NC). Results indicated a close correlation between the percentages of LGL and the capacity to bind and to lyse NC-susceptible tumor targets. In agreement with others we would thus conclude that LGL embrace the majority of NK-effector cells. The morphological definition of LGL provides an additional tool for the clinical evaluation of this cell mediated immune reactivity.