[A morphological study of lymphocyte homing in conjunctiva-associated lymphoid tissue]

High endothelial venule (HEV) is an important component of the mucosa-associated lymphoid tissue and plays a role in the homing phenomenon of lymphocytes. We investigated the presence of HEVs in conjunctiva-associated lymphoid tissue (CALT) using guinea pigs sensitized with ovalbumin. Electron microscopy showed characteristic findings for HEVs in the parafollicular area of the CALT. Lymphocytes in the vessels are trapped not only by microprocesses extending from the vascular endothelium but also by the endothelial cells. Some endothelial cells also appear to release lymphocytes. We conclude that HEVs are present also in the CALT.