Transforming growth factor-beta inhibits interferon-gamma-induced HLA-DR expression by cultured human fibroblasts

This study shows the induction of HLA-DR (DR) in fibroblasts by IFN-? and investigates the molecular mechanisms involved in the further DR down-regulation by TGF-?1. Kinetics of DR induction on human dermal fibroblasts by IFN-? showed that 1 hr of exposure was required to induce detectable levels of DR, and maximal DR expression was achieved only after 2 days of exposure to IFN-?. TGF-?1 inhibited DR induction by IFN-?, although complete inhibition never could be achieved, even with high concentrations of TGF-?1 and low concentrations of IFN-?. Inhibition was not accounted for by reduction in cell numbers, as TGF-?1 stimulated growth of the fibroblasts. Inhibition of DR induction was seen only if TGF-?1 was added during the first 24 hr of IFN-? treatment. TGF-?1 inhibited equally well if the cells were pretreated for as little as 1 hr and then washed before addition of IFN-?. TGF-?1 did not cause an overall suppression of protein synthesis. Northern blot analysis revealed that TGF-?1 greatly reduced the steady-state level of DR? mRNA induced by IFN-? at 24 hr, and then DR? transcripts became undetectable at later stages. It is concluded that early intracellular signals must build up to stimulate maximum DR synthesis, which, later on, are inactivated or degraded by the action of TGF-?1. We suggest that these mechanisms regulating DR gene transcription involve the action of genes coding for specific IFN-?-inducible transcriptional factors that are turned on and off in an expeditious manner

High-stakes testing in South Africa: friend or foe?

The Jomtien conference in 1990 on Education for All is seen by many as a turning point for the introduction of increased monitoring and evaluation of the quality of education systems around the world. Internationally, debates have arisen about the nature and frequency of assessment and its impact on education systems with its intended and unintended consequences. The phenomenon of large-scale testing is a relative latecomer to South African education. Since 1994, large-scale assessments have been implemented in core subjects such as mathematics, science and language in national and international assessments. In this paper, various forms of the large-scale assessments in South Africa are discussed in relation to high-stakes testing and their effect on the education system as a whole in the light of international experience.http://www.tandfonline.com/loi/caie20hb2016Humanities Educatio