Differences in the graft-versus-host reactivity of cells migrating through nonlymphoid tissue or lymph nodes.

Normal lymphocyte transfer reactions have been used to test the alloreactivity of lymphocytes which have migrated through lymph nodes (i.e., in efferent lymph) or nonlymphoid tissues (i.e., in afferent lymph) in sheep. Lymphocytes from afferent lymph are much less efficient at inducing a normal lymphocyte transfer lesion than lymphocytes from efferent lymph. Afferent cell preparations (which contain about 10% macrophages) do, however, cause a greater inflammatory response in the early part of the reaction, but this is at least partly nonspecific. A mixture of afferent and efferent cells produces a lesion which is simply the sum of the two expected reactions, suggesting that the afferent lymphocytes are not merely inhibited by a factor or cell in the preparation.