ABSTRACT
Thioredoxin (TRX) superfamily proteins that contain a conserved redox active site -Cys-X-X-Cys-include the proinflammatory cytokine, macrophage-migrationinhibiting factor (MIF), and the immune regulatory cytokine, glycosylation-inhibiting factor (GIF). Although they share an identical gene structure, each performs a unique biological activity. We have previously described GIF, a 13-kDa cytokine, as a product of suppressor T (Ts) cells [1,2] and a subunit of antigen-specific Ts cell factor [3,4]. Repeated injections of partially purified GIF into BDF1 mice resulted in suppression of both IgE and IgG antibody responses to ovalbumin [5]. After molecular cloning of this cytokine, however, we realized that the sequence of the coding region of human GIF cDNA [6] was identical to the sequence of human MIF cDNA [7], except for one base. In the human genome, Paralkar and Wistow [8] identified only one functional MIF-like gene whose predicted transcript sequence agreed exactly with that of human GIF cDNA, indicating that the one base difference between GIF and MIF cDNA is due to an error in sequencing. The nucleotide sequence of mouse MIF cDNA, described by Bernhagen et al. [9], is identical to the sequence of mouse GIF cDNA [6]. Thus, it appears that GIF and MIF share an identical gene in both species.
