HISTOPATHOLOGICAL CHANGES IN PRIMARY AND SECONDARY LYMPHOID ORGANS FOLLOWING CHRONIC CARBON MONOXIDE EXPOSURE

Abstract

Carbon monoxide (CO) is one of the most prevalent environmental toxicants and remains a significant cause of chronic intoxication worldwide. Long-term exposure to carbon monoxide results in persistent tissue hypoxia, oxidative stress, mitochondrial dysfunction, and inflammatory responses that adversely affect multiple organ systems. The immune system is particularly vulnerable due to its high cellular turnover and dependence on adequate oxygen supply. Chronic CO exposure induces substantial histopathological alterations in both primary and secondary lymphoid organs, including the thymus, bone marrow, spleen, and lymph nodes. These structural changes are characterized by lymphoid depletion, tissue atrophy, microcirculatory disturbances, apoptosis, and stromal remodeling. Such alterations impair immune cell maturation, proliferation, and immune surveillance functions. This review summarizes current knowledge regarding the histopathological consequences of chronic carbon monoxide exposure in lymphoid organs and discusses the underlying pathogenic mechanisms responsible for immune dysfunction.