Interleukin-l-Like Activity Constitutively Generated by Hodgkin Derived Cell Lines: I. Measurement in a Human Lymphocyte Co-stimulator Assay

Abstract

Culture supernatants (CS) from Hodgkin derived cell lines have previously been shown to contain colony stimulating activity (CSF) for human cord blood cells, fetal bone marrow and fetal liver cells. In this study 3-day CS from four Hodgkin lines (L428, L538, L540, L591) and two sublines (L428KS, L428KSA) were examined for interleukin (IL) activity. None of the tested CS supported, the growth of an IL-2 dependent murine T-cell line, suggesting that the Hodgkin lines do not produce significant amounts of IL-2. When crude 3-day CS from the various lines were assayed for IL-1-activity in the conventional murine thymocyte co-stimulator assay no or only borderline IL-1-activity was detectable. However, concentrated CS from L428KS exhibited IL-1-activity also in this assay as did lipopolysaccharide (LPS) induced human IL-1. Surprisingly, crude 3-day CS from all Hodgkin cell lines were capable of fully replacing the accessory cell requirement in ConA-induced lymphoproliferation assays of heavily monocyte-depleted human blood lymphocytes. The monocyte-depleted lymphocyte populations were obtained by 1 × g sedimentation at a sedimentation rate of 30.2 to 38.8 mm/ hr (fraction IIIa and IIIb). These cells responded poorly to the T-cell mitogen ConA at 10 υg/ ml and produced no IL-2. Addition of irradiated, autologous monocytes or of CS from the various Hodgkin cell lines quantitatively restored the ConA responsiveness and induced significant IL-2 production in the monocyte-depleted lymphocyte population, suggesting that Hodgkin lines constitutively secrete IL-1 or IL-1-like activity. A preliminary biochemical characterization (heat and pH stability, molecular weight range of 13-24 KD) supports the notion that the accessory cell replacing activity present in CS of Hodgkin cell lines is a type of human IL-1.