Origin and immunological hyporeactivity of canine alveolar lymphocytes

Autochthonous canine thoracic duct lymphocytes were isolated, labelled with 111indium and injected intravenously. Direct sampling showed that the label passed from blood to lymph within 25 hr. By gamma camera imaging, the initial accumulation of 111In the liver and spleen was followed by a striking increase in lymph node associated activity between 24-36 hr. Although initial lung-associated counts were low, a bicarbonate-induced non-specific inflammation of the right lung induced a rapid and selective accumulation of labelled lymphocytes (ratio right to left lung 8:1). Cell suspensions lavaged from the alveolar surface showed only a 9% response to phytohaemagglutinin (PHA) compared to peripheral blood lymphocytes (PBL). The addition of unfractionated lavage cells to PBL caused a macrophage-dependent suppression of mitogen responsiveness. However, macrophage depletion of alveolar lavage cells did not restore the lymphocyte response to PHA. Similarly, the frequency of alloreactive precursors of cytolytic lymphocytes (CTL) was almost 10-fold less in alveolar lymphocytes compared to PBL. Thus, bronchoalveolar lavage provides a technique by which viable cells may be recovered in significant numbers from the alveoli and should be invaluable for the investigation of lung allograft rejection.