FLUORESCENCE MICROSCOPIC STUDIES ON HEMAL LYMPH NODES IN RATS: A NEW IMMUNOBIOLOGICAL CONCEPT

Abstract

Hemal lymph nodes are characterized by a high content of blood cells most of them indifferent stages of erythrophagocytosis. These peculiar structures are not well understood up tonow regarding their functional morphology. Above all, their biological relevance, especially tothe phenomenon of disintegration of one’s own blood cells, has eluded conclusive explanation sofar. In the present study, hemal lymph nodes of 45 rats of the perirenal group were investigatedby means of confocal laser fluorescence microscopy (CLSM) in combination with threefluorescent markers: latex standard particles, liposomes and autologous erythrocytes. Eachmarker briefly entered the hemal lymph nodes when injected into the kidney, whereas no notablemigration took place after intravenous injection. Besides direct connections between hemallymph nodes and the homolateral kidney, the study also revealed lymphatic communications withthe contralateral kidney. Each marker was ingested by nodal macrophages, most of themsurrounded by red blood cells (rosette formation) and laden with the by-products of cellulardisintegration (erythrophagocytosis). Intimate contact of lymphocytes with macrophages as anexpression of special interaction (emperipolesis) between both types of cells was frequentlyobserved. A new concept is proposed, which ascribes to the hemal lymph nodes an importantimmunobiological role for the recognition of antigenic properties of one’s own red blood cellspermanently released by the kidney. The information macrophages obtain from these cells ispresented to lymphocytes, which, in turn, initiates suppresser immune reactions. Under normalconditions, this mechanism of cellular identification and surveillance serves to preserve selftolerance of the defense system against permanent renewal of one’s own red blood cellpopulation during a life time. In this way, an auto-aggressive immune anemia is circumvented.