Analytical and functional assessment of lymphoid cells within murine lung

In this study we sought to characterize the tissue leukocytes in murine lung which (when derived from peripheral lymphoid organs) have been associated with host defense against tumors and certain microbial agents. Numerical and functional properties of lung lymphoid populations obtained by collagenase digestion were evaluated in inbred mice. Flow cytometric analysis of monoclonal and polyclonal antibody labelled preparations revealed that lung cells so derived were 47% T-lymphocytes (helper-suppressor ratio 4.25), 23% B-cells (surface immunoglobulin+) and 26% asialo GM1 (natural killer) cells. Lung T-cells responded well to mitogen stimulation after partial depletion of adherent macrophages, but the magnitude of this response was less than that of autologous spleen cells. Natural killer cell (NK) activity against chromium labelled tumor target cells was also manifested by lung cells and was similar to that of peripheral spleen cells. This lung NK activity could be boosted in vitro by incubation with interferon and in vivo by treatment with poly I:C. Together, these data indicate that normal murine lung contains a large number of functional T-cell and NK cell mononuclear populations. The characterization of the cell populations presented here should facilitate future studies of their role(s) in host defense against infection and neoplasia.