The reason HTLV-1 causes the completely different neo-plastic and nervous degenerative disorders, namely ATL and HAM/TSP, remains to be elucidated. The proviral genome consists of gag, pol, and env genes, which are commonly characteristic of all retroviruses. Interestingly, the HTLV-1 genome contains a specific sequence in the 3' site of the genome designated as the pX gene, encoding alternatively a 40-kDa protein (p40 tax). In ATL, p40 tax proteins are thought to play a pivotal role in the early event of tumorigenesis. Because the proteins can transactivate some cellular oncogenes/suppressor genes, growth factor genes, and cell surface receptor genes, such as c-fos, c-myc, egr-1, p53, Bax, c-Jun, IL-2R, IL-1, IL-6, GM-CSF, TGF-P1, PTHrP, and TNF-pP] Tax, then, has the potential to immortalize lymphocytes infected by HTLV-1 in vitro. These tax-immortalized cells are usually still IL-2-dependent, so that other cellular events such as p53 and p16 mutations are required to transform these cells. In fact, most ATL demonstrate either p53 or p16 mutation in clinical samples.
However, in degenerative and inflammatory disorders such as HAM/TSP and uveitis, slow viral infection, cellmediated immunity, and an aberrant cytokine network are possible pathogenic mechanisms. Recently, circulating CD8+ cytotoxic T-cells specific for HTLV-1 pX have been notably found in patients with HAM/TSP. Furthermore, susceptibility to HAM/TSP is considered to be determined by host immunogenetic factors such as HLA haplotypes linked to HTLV-1 responsiveness.
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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.