Identification of a T cell hybridoma that produces large quantities of macrophage-activating factor.

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Abstract
A murine T cell hybridoma, constructed by fusion of alloantigen-activated T cells with the BW5147 T cell lymphoma, which produces a lymphokine capable of inducing tumoricidal activity in macrophages, was identified. Lymphokine release was detected only after mitogen stimulation of the T cell hybridoma culture. Upon cloning of the parental hybridoma, 24 of 27 clones prodouced tumoricidal-inducing activity. Seven clones produced more cytocidal-inducing activity than did conventional supernatants, generated by concanavalin A stimulation of normal murine spleen cell cultures, which contained macrophage-activating factor (MAF). The supernatant of hybridoma clone 24/G1 was 25 times more active than conventional MAF preparations. Using supernatants from a variety of clones, the levels of macrophage-activating activity and interleukin 2 varied independently of one another. The lymphokine produced by hybridoma clone 24/G1 appeared to be identical to conventional MAF by a variety of criteria including the following: a requirement for a 2nd signal for induction of tumoricidal activity in macrophages; inactivation after incubation for 1 h at 65.degree. C; loss of activity after treatment at pH 4.0 but not at pH 5.0. Like conventional MAF, the hybridoma MAF eluted as a single peak after molecular sieve chromatography on Sephadex G100 and exhibited an apparent MW of 55,000. Although somewhat heterogeneous, the majority of hybridoma 24/G1 MAF displayed an isoelectric point of 5.4 as determined using the chromatofocusing technique. These results illustrate the usefulness of T cell hybridomas in distinguishing between various lymphokine activities and indicate that the T cell hybridoma clone 24/G1 will be of particular usefulness in achieving the biochemical purification of substantial quantities of murine MAF.