PURPOSE: Peroxiredoxin-2 (PRDX-2) is an antioxidant and chaperone-like protein 
critical for cell function. This study examined whether the levels of lymphocyte 
PRDX-2 are altered over 1 month following ultra-endurance exercise.
METHODS: Nine middle-aged men undertook a single-stage, multi-day 233 km (145 
mile) ultra-endurance running race. Blood was collected immediately before 
(Pre), upon completion/retirement (Post), and following the race at Day 1, Day 7 
and Day 28. Lymphocyte lysates were examined for PRDX-2 by reducing and 
non-reducing SDS-PAGE with western blotting. In a sub-group of men who completed 
the race (n = 4), PRDX-2 oligomeric state (indicative of redox status) was 
investigated.
RESULTS: Ultra-endurance exercise caused significant changes in lymphocyte 
PRDX-2 (F(4,32) 3.409, p = 0.020, η(2) = 0.299): 7 days after the race, PRDX-2 
levels in lymphocytes had fallen to 30% of pre-race values (p = 0.013) and 
returned to near-normal levels at Day 28. Non-reducing gels demonstrated that 
dimeric PRDX-2 (intracellular reduced PRDX-2 monomers) was increased in three of 
four race completers immediately post-race, indicative of an 'antioxidant 
response'. Moreover, monomeric PRDX-2 was also increased immediately post-race 
in two of four race-completing subjects, indicative of oxidative damage, which 
was not detectable by Day 7.
CONCLUSIONS: Lymphocyte PRDX-2 was decreased below normal levels 7 days after 
ultra-endurance exercise. Excessive accumulation of reactive oxygen species 
induced by ultra-endurance exercise may underlie depletion of lymphocyte PRDX-2 
by triggering its turnover after oxidation. Low levels of lymphocyte PRDX-2 
could influence cell function and might, in part, explain reports of 
dysregulated immunity following ultra-endurance exercise.