Memory and CD8⁺ are the predominant bovine bronchoalveolar lymphocyte phenotypes

Bovine lymphocytes obtained by bronchoalveolar lavage (BAL) of healthy calves were simultaneously analyzed and compared to peripheral blood lymphocytes using monoclonal antibodies specific for bovine leukocyte differentiation antigens. Phenotypic differences were observed between bronchoalveolar and peripheral blood T-lymphocyte subpopulations, demonstrating selective lymphocyte migration to the bovine lung. The bronchoalveolar and peripheral blood T-lymphocyte populations, defined by expression of CD2, were similar, but bronchoalveolar T lymphocytes were predominately CD8⁺ while peripheral blood T cells were predominately CD4⁺. In addition, memory lymphocytes, characterized by low expression of CD45R and activated lymphocytes (CD25⁺), were found in significantly higher proportions in the bronchoalveolar compartment. The proportion of γδ T lymphocytes was, however, significantly higher in peripheral blood. B cells were observed in similar proportions in the bronchoalveolar compartment and peripheral blood.