Studies on the lymphocytes of sheep. IV. Migration patterns of lung-associated lymphocytes efferent from the caudal mediastinal lymph node.

Small lymphocytes from the efferent lymph of the caudal mediastinal lymph node (CMLN), the regional node of the lower respiratory tract, were labelled in vitro either with 51Cr, or with the fluorochrome rhodamine isothiocyanate. The labelled lymphocytes were washed and returned to the sheep by intravenous (i.v.) injection; their later appearance in the lymph from the CMLN was monitored, as was their appearance in lymph from either a peripheral somatic lymph node (PSLN) or the intestinal lymph duct. It was found that the labelled lymphocytes entered the lymph from the CMLN and PSLNs with equal facility but were significantly less able to enter the intestinal lymph. Similarly, the large lymphocytes (immunoblasts) which were released into the lymph after antigenic stimulation of the CMLN, and which were labelled in vitro with [125I]Udr, showed little tendency to enter the gut after i.v. injection and became distributed throughout the body in the same way as immunoblasts efferent from the PSLN, i.e. they went principally to the lungs, and spleen.