ASSOCIATION OF NEUTROPHILS WITH HIGH ENDOTHELIAL VENULES IN THE NEONATAL RAT LYMPH-NODES - A PROBABLE RELATION TO IMMUNOINCOMPETENCE

The endothelium of the high endothelial venules (HEVs) of lymph nodes is normally considered to inhibit an association with neutrophils. The present paper shows that for a few weeks after birth, however, neutro phils are commonly associated with the walls of HEVs, the extent depen ding on the site of the lymph node. Overall, neutrophils increase in n umbers in rat nodes from birth until about day 11, and vanish progress ively thereafter. Moreover, neutrophils are more abundant in the nodes of standard neonates than in the nodes of pathogen-free neonates rais ed in an aseptic milieu. It is concluded that the postnatal recruitmen t of neutrophils by nodal HEVs relates to the then prevailing state of immaturity of the immune system. An explanation is proposed as to why neonatal HEVs of nodes recruit neutrophils and not only lymphocytes, as is the case later in ontogeny.