Histogenesis of in-vivo rosettes with particular reference to immunological tolerance

Certain lymphoid tissues appeared reddish in both laboratory animals and man. Among other areas, they were constantly found around the renal hilum and these had been termed renal hemolymphoid tissues (RHLT). Abundant sinus erythrocytes and leukocytes further characterized these anomalous structures. Previously, we described that erythrocytes and leukocytes gained significant entry into these organs via the afferent lymphatics. The present work extended that study by tracing the histogenesis of the macrophage-erythrocyte-rosettes (MER) within these structures. At the peripheral sinus, red cells were mostly freely suspended in the tissue fluid. After passing through the dense lymphoid tissue area to the deep sinus, most erythrocytes organised radially around the margins of the macrophages in the form of rosettes. Since rosettes formation is widely used routinely as in-vitro technique, we designed a rapid intravenous approach that fixed all tissues and organs in-situ and studied them by both light and electron microscopy. We found that the peripheral sinus had freely suspended erythrocytes which retained their typical biconcave shape. At the deep sinus, rosetting red cells commonly assumed comma or spindle shapes. Besides, abundant debris and hemosiderin granules were present within the cytoplasm of the MER macrophages. The specific polar orientation of the erythrocytes along the margins of the leukocytes and active formation of cytoplasmic processes by the macrophages suggested in-vivo loss of self-tolerance between the two autologous cell populations.