He. Castenholz et A. Castenholz, FLUORESCENCE MICROSCOPIC STUDIES ON HEMAL LYMPH-NODES IN RATS - A NEWIMMUNOBIOLOGICAL CONCEPT, Lymphology, 29(4), 1996, pp. 141-150
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.