Characterization of normal human lung lymphocytes and interleukin-2-induced lung T cell lines

Lymphocytes from the lower respiratory tract were obtained by bronchoalveolar lavage of healthy, non-smoking individuals. Various monoclonal antibodies characterizing activated T cells, helper-inducer and suppressor-inducer T cell subsets, and naive versus memory cells were used to define the phenotype of these lymphocytes. The highly variable CD4/CD8 ratio (0.3 to 6.6; mean = 2.1) and the large proportion of the T cells expressing HLA-DR (9 to 38%; mean = 21%) suggested that the T cells were recently activated by antigens selectively stimulating either helper or cytotoxic/suppressor T cell function. Indeed, the CD45RA antigen, a marker characteristic of suppressor-inducer T cells when coexpressed with CD4, and naive T cells in general, was absent from T cells in most preparations (0 to 17%; mean = 5%), while the CD45RO antigen, a marker of memory cells and immature thymocytes, was present on 68 to 100% of all lung T cells. The majority (greater than 70%) of the CD4+ helper T cells was CD45RO+ CD45RA-, a phenotype found on T cells that provide help for B cell immunoglobulin synthesis. Lung T cells proliferated poorly in response to phytohemagglutinin and concanavalin A but did respond to activation with low concentrations of anti-CD3 mAb (2 to 25 ng/ml) and to interleukin-2 (IL-2) alone to similar extent as did autologous peripheral blood lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)