Formaldehyde (FA) is widely used in several industries and medical applications. Healthcare workers, anatomy instructors and medical students are considered as high-risk population. FA induces alterations in the immune system as immune turbulences and even immunosuppression that consequently increases the progression of cancer or allergies.
The ongoing debates surrounding FA-induced spleen toxicity necessitate additional analysis. Therefore, we studied the probable toxic effects of FA and subsequent histological, immune-histochemical and morphometric changes on the spleen. Forty adult male albino rats were assigned to four groups; control group (I), groups (II, III, IV) were exposed to 10% FA inhalation for 18 weeks in different doses. Spleen specimens were processed and stained using hematoxylin & eosin, CD4, CD8 and Bcl-2 immuno-staining. All experimental groups showed thicker connective tissue capsules, congested dilated blood sinusoids. Group (II) revealed a significant disruption in the histological structure. Lymphoid cells were degenerated with pyknotic nuclei and vacuolated cytoplasm. Some follicles exhibited necrotic germinal centers. These findings were more noticeable in groups (III, IV). Groups (III, IV) presented sinusoidal hemorrhage and megakaryocytes infiltrations. The experimental groups showed an increase in the positive immune expression of CD4, CD8 and Bcl-2. White pulp and germinal center measurements were decreased in experimental groups. Groups (II, III) displayed increased marginal zone diameter, while group (IV) showed its decrease. Mantle layer and PALS diameters decreased in group (II), and then increased in groups (III, IV). FA can induce harmful effects on the spleen through modifying CD4, CD8 and Bcl-2 in dose-dependent manner.