Objective: To characterize cytokine profiles and lymphocyte subpopulations in lung parenchyma and bronchoalveolar lavage (BAL) fluid from normal bovine lungs.
Animals: Eight 12- to 18-month-old cattle.
Procedure: Cell populations in BAL fluid and collagenase-digested lung parenchyma were analyzed by flow cytometry and monoclonal antibodies. Proportions of total cell populations were determined, using Giemsa-stained cytospots. Distribution of lymphocytes within the lung parenchyma was analyzed by immunohistochemistry, and cytokine mRNA species in the parenchyma were characterized by use of reverse transcriptase-polymerase chain reaction analysis.
Results: Cytokine profiles indicated high amounts of mRNA for interleukins 6 and 10 and transforming growth factor beta. In the BAL fluid and lung parenchyma, macrophages were the predominant cell type, although the proportion was lower in the parenchyma. Lymphocytes made up approximately 3% of both cell populations. Common to both lung compartments was the predominance of CD2+ and gamma delta T cells over B lymphocytes. There were more CD8+ T cells than CD4+ T cells in both compartments. The gamma delta cells made up approximately 9% of the lymphocyte populations. Two-color flow cytometry revealed CD8+ gamma delta T cell and CD8+CD5- populations that were unique to BAL fluid. In the BAL fluid and parenchyma, most CD4+ and CD8+ T cells expressed high amounts of CD44, a characteristic of memory T cells. The gamma delta T cells were CD44(10), as were B cells in the lung parenchyma. The B cells from BAL fluid expressed high amounts of CD44. Immunohistologic analysis of lung tissue revealed bronchus-associated lymphoid tissue structures with distinctive germinal center organization of B cells encompassed by CD4+ T cells.
Conclusions: Results provided normal values for comparison with those of other species and with the bovine respiratory tract response to disease.