Corticotropin-Releasing Hormone (Crh) Expression in the Thymus Gland of the Lewis Rat: Effect of Collagen-Induced Arthritis

Thymus glands and peripheral lymphocytes are known to express CRH This study addresses 1) the distribution of ir-CRH in thymus sections, and 2) the effect of immune challenge (collagen-induced arthritis, CIA) on CRH expression. CIA was induced in 14 female Lewis rats, with 7 exposed to stress (5 hrs/day) on days 7-13 post-injection. Stress retarded, but did not prevent, progression of arthritic symptoms: at sacrifice (day 15 post-injection) there was no difference in symptom severity. Thymus weights in CIA groups were less than in uninjected rats (p\u3c0.05, non-stress; p\u3c0.005 stress). In thymus sections, most irCRH localized to discrete cell clusters. Cells with the appearance of lymphocytes were most heavily stained and immunoreactivity was frequently more dense near the plasma membrane. Vessels were seen in the center of many these clusters and extravasating cells appeared densely stained In rats with CIA (non-stressed), the ir-CRH clusters appeared larger and more diffuse. In stressed rats with CIA, ir-CRH was more intense relative to the non-stress animals with arthritis. We conclude that selected subsets of lymphocytes express CRH during maturation and that CRH expression in the thymus is regulated by immune challenge and factors associated with stress