Human Large Granular Lymphocytes Are Potent Producers of Interleukin-1

Natural killer (NK) activity against tumour and virus-infected target cells is shown by a subpopulation of peripheral blood mononuclear leukocytes with the morphological features of large granular lymphocytes (LGL). The lineage of human LGL is still controversial, as they display surface markers of both T lymphocytes and myelomonocytic cells. LGL have recently been reported to produce lymphokines such as interleukin-2 (IL-2) and alpha- as well as gamma-interferons, functions associated mainly with T cells. To determine whether cytokines associated with other cell lineages are also produced by LGL, we examined whether they might produce a myelomonocyte -associated cytokine such as interleukin-1 (IL-1). IL-1 is a 12-18,000 molecular weight (MW) lymphokine produced by a variety of cell types such as monocytes, keratinocytes and a human dendritic cell line, which plays a crucial role in immunoregulation and inflammation. Moreover, IL-1 has recently been reported to act synergistically with IL-2 and interferons in boosting LGL-mediated NK activity. We now show that a subset of highly purified human LGL with NK activity can be stimulated to secrete a soluble factor with the biochemical and biological characteristics of human IL-1.