Age-related morphological and histological changes in the dromedary camel thymus

The thymus is a key lymphoid organ responsible for T-cell development, yet information on its postnatal dynamics in the dromedary camel remains limited. In this study, we examined age-related morphological and histological changes in the camel thymus across four age groups (up to 1 year, 1-3 years, 3-5 years, and over 5 years) using fixed and fresh anatomical samples and stained paraffin-embedded sections. The thymus consisted of cervical and thoracic parts, with the thoracic thymus reaching its maximal size shortly before or at one year of age and achieving its greatest weight at one year, followed by a progressive decline thereafter in size, accompanied by increasing fat infiltration. Histologically, advancing age was associated with thickening of the interlobular septa, reduced lobular diameter, and the progressive replacement of parenchymal tissue with fibrous and adipose components, and keratinization or degeneration of Hassall's corpuscles. While the number of Hassall's corpuscles peaked in 1-3-year-old camels and declined thereafter, their thickness increased progressively across age groups. Collectively, these findings indicate an early onset of thymic maturation followed by gradual involution in the dromedary camel, providing valuable insight into the timeline and structural basis of immunosenescence in this species.