Comparison of mononuclear cell subpopulations in bronchoalveolar lavage fluid in acute rejection after lung transplantation and Mycoplasma infection in rats.

Acute lung rejection after orthotopic left lung transplantation and Mycoplasma pulmonis infection were studied immunohistologically by bronchoalveolar lavage (BAL) in inbred rats using monoclonal antibodies differentiating lymphocyte and macrophage subpopulations. Twenty transplants in a major histocompatibility complex (MHC)-different strain combination (Brown-Norway/Lewis) were examined 2, 4, and 6 days after transplantation. Thirty isotransplants (Lewis/Lewis) and normal Lewis rats were used as controls. Eight Lewis rats with acute Mycoplasma pulmonis infection and six Lewis rats with chronic Mycoplasma infection also underwent BAL. Mononuclear cell subpopulations were analyzed using a panel of monoclonal antibodies to MHC and macrophage differentiation antigens: ED1 monocyte/macrophages, ED2 inflammatory tissue macrophages, OX19 T lymphocytes, and OX12 B lymphocytes. The following results were obtained: (1) All allotransplants developed acute rejection on day 2, and it advanced until day 6, demonstrating severe perivascular and peribronchiolar infiltration of inflammatory tissue macrophages (ED1+/ED2+): (2) the proportion and number of inflammatory macrophages (ED2+) in BAL fluid increased on day 6; (3) in BAL the proportion and number of T lymphocytes (OX19+) increased more prominently than B lymphocytes (OX12+) on day 6 of acute rejection; (4) in infection with Mycoplasma pulmonis the increase of T lymphocytes (OX19+) in BAL was more prominent than that of B lymphocytes (OX12+). In conclusion, serial analysis of macrophage, T- and B-lymphocyte antigens was performed. The increase of the proportion of inflammatory macrophages (ED2+) and lymphocytes (OX19+, OX12+) in BAL fluid occurred rather late in the rejection response. This limits the use of BAL as an early diagnostic method of allografted lung rejection.(ABSTRACT TRUNCATED AT 250 WORDS)