The effects of antigen on the migration of recirculating lymphocytes through single lymph nodes

The flow of blood to lymph nodes and its relation to lymphocyte traffic and the immune response

The blood flow to individual lymph nodes of sheep and rabbits has been determined with 85Sr-labeled microspheres. A popliteal node of the sheep received 0.014% of the cardiac output and a comparable node in the rabbit 0.011%. A sheep lymph node weighing 1 g received an average of 24 ml/h of blood. It was calculated that there was a highly selective removal of lymphocytes by the node and that an equivalent to one in every four lymphocytes that entered a normal lymph node migrated out of the blood, through the substance of the node, and into the efferent lymph. During the immune response to either allogeneic lymphocytes or tuberculin, the blood flow to sheep lymph nodes, even without considering the increase in node weight, increased an average of fourfold. During the primary immune response in the rabbit to keyhole limpet hemocyanin, the blood flow increased threefold. The increase in blood flow preceded the antigen-induced increase in lymphocyte traffic recorded in the efferent lymph. The early phase of increased blood flow was considered to be due to hyperemia, whereas the latter phase had a significant angiogenesis component. It was calculated that an equivalent to 60% of the entire mobilizable pool of lymphocytes could pass through an average lymph node in the blood during an immune response lasting 5 days.

Age-related changes in localization of injected radiolabelled lymphocytes in the lymph nodes of antigen-stimulated mice

The localization of i.v. injected syngeneic lymph node cells, radiolabelled with 51Cr or 75Se-L-selenomethionine, was studied in male CBA/H mice aged between 3 and 30 months. The following results were obtained. (1) Localization of cells from young adult donors was greater in the s.c. lymph nodes of old than of young recipients, the main increase being between 15 and 17 months of age. Increases in lymph node weight and DNA-synthesis were also seen at this time; but the rise in cell localization was significant even when calculated per unit of tissue weight. Splenic localization either declined slightly with age or, like the liver, showed no significant change. (2) Local antigenic stimulation by a single injection of sheep erythrocytes into one front footpad, 24 hr before lymph node cell injection, resulted in increased localization in the regional lymph nodes of 3-17 month old, but rarely of 24-30 month old mice. (3) No consistent differences in localization were observed between lymph node cells from 4-month and 25-month old donors. Both age-related and antigen-related increases in cell localization were at least partly attributable to an enhanced rate of entry of lymphocytes from the blood to the lymph nodes. Although the changes underlying the decline in antigen-related localization of cells in old recipients have still to be clarified, it is probable that the defective immune responses of old mice result partly from this decline.