T Cell Growth Factor: Parameters of Production and a Quantitative Microassay for Activity

TLDR

Several soluble factors have been linked to the proliferation and differentiation of thymus‑derived lymphocytes, and one such factor present in medium conditioned by T cell mitogen‑stimulated lymphocytes promotes long‑term culture of normal and antigen‑specific cytotoxic T cells. The authors present a sensitive microassay that detects this proliferative stimulus by measuring tritiated‑thymidine incorporation in continuous murine tumor‑specific cytotoxic T cell lines. The assay uses microliter quantities of sample fluid and tritiated‑thymidine incorporation in CTLL, enabling quantitative analysis of T cell growth factor activity. The assay demonstrated that T lymphocytes are required for T cell growth factor production and that the factor is actively removed from culture medium by proliferation of either T cell mitogen‑activated lymphocytes or CTLL.

Abstract

Several soluble factors have recently been associated with the proliferation and differentiation of thymus-derived lymphocytes. One of these factors present in medium conditioned by T cell mitogen-stimulated lymphocytes has the ability to promote the long-term culture of normal and antigen-specific cytotoxic T cells. We report a method to test for this proliferative stimulus in the form of a sensitive microassay based upon the tritiated-thymidine incorporation of continuous murine tumor-specific cytotoxic T cell lines (CTLL). The microassay requires microliter quantitites of sample fluid and is amenable to quantitative analysis. This highly reproducible, quantitative assay for T cell growth factor (TCGF) has allowed investigation as to the kinetics of TCGF generation and has revealed that T lymphocytes are required for its production. Further investigation has supported the notion that this nonspecies-specific factor is actively removed from tissue culture medium by the proliferation of either T cell mitogen-activated lymphocytes or CTLL.