FLUORESCENCE MICROSCOPIC STUDIES ON HEMAL LYMPH-NODES IN RATS - A NEWIMMUNOBIOLOGICAL CONCEPT

Hemal lymph nodes are characterized by a high content of blood cells m ost of them in different stages of erythrophagocytosis. These peculiar structures are not well understood up to now regarding their function al morphology. Above all, their biological relevance, especially to th e phenomenon of disintegration of one's own blood cells, has eluded co nclusive explanation so far. In the present study, hemal lymph nodes o f 45 rats of the perirenal group were investigated by means of confoca l laser fluorescence microscopy (CLSM) in combination with three fluor escent markers: latex standard particles, liposomes and autologous ery throcytes. Each marker briefly entered the hemal lymph nodes when inje cted into the kidney, whereas no notable migration took place after in travenous injection. Besides direct connections between hemal lymph no des and the homolateral kidney, the study also revealed lymphatic comm unications with the contralateral kidney. Each marker was ingested by nodal macrophages, most of them surrounded by red blood cells (rosette formation) and laden with the by-products of cellular disintegration (erythrophagocytosis). Intimate contact of lymphocytes with macrophage s as an expression of special interaction (emperipolesis) between both types of cells was frequently observed. A new concept is proposed, wh ich ascribes to the hemal lymph nodes an important immunobiological ro le for the recognition of antigenic properties of one's own red blood cells permanently released by the kidney. The information macrophages obtain from these cells is presented to lymphocytes, which, in turn, i nitiates suppresser immune reactions. Under normal conditions, this me chanism of cellular identification and surveillance serves to preserve self-tolerance of the defense system against permanent renewal of one 's own red blood cell population during a life time. In this way, an a utoaggressive immune anemia is circumvented.