Most human pulmonary infiltrating lymphocytes display the surface immune phenotype and functional responses of sensitized T cells

Pulmonary infiltrating lymphocytes (PIL) isolated directly from human lung were examined for their surface immune phenotype by monoclonal antibody staining and cytofluorimetry. In order to purify PIL, resected lungs were enzymatically digested with collagenase and DNase and subjected to density centrifugation and nylon-wool column separation. In some cases, CD4+ lymphocytes were further purified with αCD8 and complement. The majority of pulmonary lymphocytes were CD2+ (87 ± 1%) and CD3+ (73 ± 4%). Virtually all of the CD3+ PIL were Tiαβ+. Greater than 90% of both CD4+ or CD8+ PIL were CD45RO+ and CD45RA−, consistent with prior antigen sensitization in vivo. A subset of CD4+ PIL (34 ± 4%) expressed Leu8, the human congener of the murine MEL-14 lymphocyte homing receptor, whereas most homologous CD4+ peripheral blood lymphocytes were Leu8+ (75 ± 8; P < 0.01). HLA-DR surface antigens were expressed by 45 ± 5% of CD4+ PIL versus 9 ± 1% of CD4+ peripheral blood lymphocytes (P < 0.001). There was no significant...