Edston E, et al. - Researchers conducted histochemical and immunohistochemical evaluation of samples from thymus glands from 283 autopsy cases and performed a comparison of a subpopulation of 41 intravenous drug addicts with age-matched control cases. Findings revealed an accelerated involution of the thymus in the 20- to 25-year interval and thereafter the involution occurred at a steady pace of 5% per year. Also, there was a successive decline in the size of Hassall bodies. Relative to controls, drug addicts displayed an increased dystrophic calcification of the Hassall bodies and had a significant difference in thymus size (atrophy). Moreover, the relative numbers of CD4 and CD8 lymphocytes differed in the two, where CD4+ cells were reduced in drug addicts. As per their hypothesis, the reduction of CD4+ lymphocytes and thymic hypotrophy in this population could be due to the signs of hepatitis C virus infection that was found in the majority of drug addicts and the reduced number of functionally intact Hassall corpuscles.