Homing and in situ differentiation of resident pulmonary lymphocytes
Sim, Gek-Kee ; Rajaserkar, Ramanujam ; Dessing, Mark ; Augustin, Andrei
In: International Immunology, 1994, vol. 6, no. 9, p. 1287-1295
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- At birth, T lymphocytes which colonize the lung are mainly of the γδ subset, while αβ T cells predominate in the spleen. Thus, the lung is a preferred site for the homing of γδ T cells in the perinatal period. However, after birth, the pattern of Vγ gene usage among resident pulmonary lymphocytes (RPL) changes with age, from a predominance of Vγ6 at birth to a predominance of Vγ4 in older mice. The generation of the Vγ6 fraction appears to be thymus dependent, since in athymic nude mice, the Vγ6 population present at birth is replaced by Vγ4 T cells. In the postnatal period, both RAG-1 and RAG-2 genes are expressed at high levels in the RPL population. TCR bearing cells are among those that express RAG genes, indicating that maturation of T cells takes place in this organ. In addition, transfer experiments reveal that lymphoid precursors are present in the lung. The stage of differentiation of these precursors will be characterized in future studies. The data presented here indicate that pulmonary T lymphocytes are derived from both migrants of thymic origin and from precursors which have undergone differentiation and selection in the lung. The population that is generated in situ and that has not been selected in the thymus may include cells that are typical for the pulmonary environment