Humoral immune responses within the lung of bone marrow transplant recipients studied by bronchoalveolar lavage.

We investigated 20 bone marrow transplant recipients with pneumonitis using bronchoalveolar lavage (BAL) to assess the humoral immune response in the lung. We measured the levels of total IgG, IgM and IgA in bronchoalveolar lavage fluid and serum, and albumin measurements were used to correct for simple diffusion of immunoglobulins from serum into the lung. We found evidence for the local production of immunoglobulins G, M and A in 15 patients. This was independent of the cause of the pneumonitis. We also found that, although seven patients who recovered from their pulmonary problem had evidence of considerable local production of immunoglobulin, eight patients who died were also producing immunoglobulins in the lung. Death due to pneumonitis in BMT recipients cannot, therefore, be ascribed to a failure of the local humoral immune response.