Effects of thymulin 5cH in granuloma evolution and B1 cell differentiation: an experimental model to understand its biological mechanisms

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In previous studies, we found that thymulin (a thymic hormone), when prepared in homeopathic 5cH potency, had the property to improve the productive performance of broiler chickens infected with reovirus, as well as modulate the development of Ehrlich tumor and granuloma inflammatory lesions in mice by immune-mediated mechanisms. The aim of the present work was to study the immunomodulatory mechanisms of thymulin 5cH in a granuloma experimental model, by subcutaneous inoculation of BCG in mice, focusing the B-1 cells and zinc involvement in this process. Three groups of male Balb/c SPF mice (group A treated with thymulin 5cH, group B treated with thymulin 5cH incubated in Chelex ® - a zinc chelant - and group C, control, treated with vehicle) were inoculated with BCG in the left footpad and subcutaneous granuloma and spleen were harvested for histomorphometry analysis, after 7, 14 and 21 days. Ziehl-Neelsen, HE and Prussia Blue staining methods were used. Flow cytometry was also used in the same times to characterize and quantify peritoneal cells. Positive cells for CD11b (activated phagocytes, B-1 cells), CD19 (B-1 and B-2 cells), CD23 (negative B-1 cells, positive B2 cells) and CD5 (B-1a cells) were analyzed in a FACS Calibur (BD) device. Statistical analysis was performed using Kruskal - Wallis / Dunn for nonparametric evaluations and ANOVA / Tuckey-Krammer for the parametric ones. The X² method was used to evaluate the cell count in flow cytometry. P values ≤ 0.05 were considered statistically significant. Mice treated with thymulin 5cH presented higher macrophage activity and increase in the follicular area were seen in spleen after 7 days. Increase in gross lesion diameter and decrease in local BCG infection were seen after 21 days. At this time, the flow cytometry demonstrated the increase in peritoneal phagocytes derived from B-1 cells in thymulin 5cH treated mice, independently of Chelex ® incubation. The incubation of thymulin 5cH with Chelex ® blocked its effects only upon the number of B2 cells in the peritoneum and reduces Mn levels in the medicine solution. We conclude that thymulin 5CH modulates the BCG-induced granuloma through more than one mechanism, especially by peritoneal B1 cell differentiation into phagocytes.