Histopathological Study of Changes in White-Pulp Structure Due to Lymphoid Depletion in the Spleen in Male Rats Caused by Exposure to Transitional Cigarette Smoke

Conventional cigarette smoke and electronic cigarette vapor contain toxic compounds that may impair immune function, particularly in the spleen. This study evaluated histopathological changes in the spleen in male white rats (Rattus norvegicus, <i>n</i> = 32) divided into four groups: control, conventional-cigarette smoke (CCS), electronic cigarette vapor (ECS), and transitional cigarette smoke (TCS). The TCS group was sequentially exposed to CCS for 15 days followed by ECS for 15 days, with twice-daily exposure. Spleen tissues were analyzed semi-quantitatively using ImageJ and statistically using the Kruskal-Wallis test after Shapiro-Wilk normality testing. Comparisons among the four groups showed significant differences in necrosis (<i>p</i> = 0.025) and vascular degeneration (<i>p</i> = 0.027). In contrast, hemosiderin, congestion, stretching, and vacuolization parameters did not show statistically significant differences among groups (<i>p</i> > 0.05). These findings suggest that switching from conventional cigarettes to e-cigarettes does not protect against splenic damage and may exacerbate immune dysfunction due to cumulative toxic exposure.