Structural changes in the lacrimal sac epithelium and associated lymphoid tissue during experimental dacryocystitis

PURPOSE To examine structural changes in the lacrimal sac epithelium and associated lymphoid tissue of rabbits with experimentally induced dacryocystitis. METHODS Experimental dacryocystitis was induced by an inoculation of Staphylococcus aureus into the lacrimal sac. The histological changes of the inflamed lacrimal sac epithelium and associated lymphoid tissue were studied by light and electron microscopy. RESULTS After 1 month, numerous inflammatory cells (CD20-positive B lymphocytes, CD3-positive T lymphocytes, IgA-positive plasma cells, and polymorphonuclear leukocytes) infiltrated the lamina propria and the epithelium overlying the diffuse lymphoid tissue. Three months later, the density of the infiltrated leukocytes was markedly decreased. The epithelial lining overlying the diffuse lymphoid tissue became thicker with numerous secretory granules in the supranuclear regions. CONCLUSION The lacrimal sac epithelium and associated lymphoid tissue play a major role in the defense mechanism during inflammation. Overproduction of secretory granules after bacterial inoculation could enhance the antimicrobial defense.