Distribution of lung-associated lymphocytes from the caudal mediastinal lymph node: effect of antigen.

Lymphocytes from the efferent lymph of the caudal mediastinal lymph node (CMLN) were labelled in vitro with 125I-iododeoxyuridine [125I]UdR and Na2(51)CrO4. The labelled cells were re-infused i.v. and their distribution in organs/tissues was determined 20-24 hr later. As indicated by tissue 125I-activity, pulmonary lymphoblasts had a marked tendency to relocate in the lung, regional pulmonary lymph nodes and spleen. Localization of efferent CMLN lymphoblasts was greater in antigenically stimulated segments compared to unstimulated segments of the lung. Dual antigen experiments indicated that the increased localization was not specific for the antigen which stimulated production of lymphoblasts used for in vitro labelling and reinfusion. Intranodal labelling of blasts by the direct injection of [125I]UdR supported the results obtained from in vitro labelling. In these studies, comparisons were made with the localization of lymphocytes obtained from thoracic duct lymph.