Mononuclear Cells From Human Lung Parenchyma Support Antigen‐Induced T Lymphocyte Proliferation

Abstract

We have previously demonstrated that there is a subpopulation of loosely adherent pulmonary mononuclear cells that can be isolated from minced and enzyme‐digested lung tissue with a potent capacity to stimulate allogeneic T lymphocyte proliferation. We now demonstrate that these cells are also capable of stimulating an autologous mixed leukocyte reaction (AMLR) and presenting antigen to autologous T lymphocytes. These loosely adherent mononuclear cells (LAM) were more effective than either alveolar macrophages or monocytes as antigen‐presenting cells. Depletion of phagocytic or Fc receptor‐positive cells from the LAM population enhanced the stimulation of an reaction AMLR while preserving antigen‐induced T lymphocyte proliferation. These results indicate that there are nonphagocytic, Fc receptor‐negative accessory cells in human lung parenchyma capable of activating resting T cells in an AMLR and supporting antigen‐specific T lymphocyte proliferation. The identity of these cells is uncertain, but the data strongly suggest that the cell is not a classical monocyte‐derived macrophage. These antigen‐presenting cells may be critical in the initiation of immune responses within the lung.