From ScienceDaily: "Premature aging of the immune system appears to play a role in the development of amyotrophic lateral sclerosis (ALS) ... CD4+ T cells, which grow and mature in the thymus before entering the bloodstream, are reduced in number in patients who have ALS as the thymus shrinks and malfunctions. ... The thymus gland, where immune cells called T lymphocytes mature before entering the bloodstream, normally reaches its peak in size and production in childhood. It then slowly shrinks, becoming virtually nonexistent in the elderly, but the lifespan of newly produced T cells ranges from three to 30 years. This study found that the thymus glands of mice and patients with the disease undergo accelerated degeneration. ... The findings are consistent with evidence collected over a decade [suggesting] that a well-functioning immune system plays a pivotal role in maintaining, protecting and repairing cells of the central nervous system. Studies conducted in animals have shown that boosting immune T-cell levels may reduce symptoms and slow progression of certain neurodegenerative diseases. ... If T-cell malfunction is confirmed to be a contributing factor to ALS, as we propose, therapeutic strategies may be aimed at overcoming this deficiency through rebuilding, restoring or transplanting the thymus."