Abstract: | Thyroid tissues containing lymphoid secondary follicles were studied immunohistochemically for the presence of acid cysteine proteinase inhibitor (ACPI). Reticulum cells in the lymphoid secondary follicles, mainly dendritic reticulum cells, exhibited a positive reaction. In addition, in 2 cases a positive reaction could be detected in some of the thyroid epithelial cells, adjacent to the lymphoid secondary follicles. The possible function of ACPI generally and its role in the function of those cells containing it, is discussed. |