Lymphocyte subpopulations in middle ear effusions: Flow cytometry analysis

Objective: The aim of this study was to identify lymphocyte subpopulations in middle ear effusions, peripheral blood, and adenoids in children suffering from otitis media with effusion. Setting: Tertiary referral center. Patients: Thirty-three children (55 ears) undergoing myringotomy for otitis media with effusion. Methods: CD3(+), CD4(+), CD8(+), CD19(+), and natural killer cell populations were investigated in middle ear effusion, peripheral blood, and adenoids using a three-color monoclonal antibody and flow cytometry method for quantitative estimation. Results: T cells (CD3(+)) are dominating lymphocytes in middle ear effusion. Among T lymphocytes, the majority are those of the helper type (CD4(+)). The dominating isoform among CD4(+) lymphocytes are memory cells (CD4(+)CD45RO(+)); among CD8(+) lymphocytes, naive cells (CD8(+)CD45RA(+)). The percentage of CD4(+) cells, CD8(+) cells, and the CD4(+)/CD8(+) ratio was significantly higher in middle ear effusions than in blood. The percentage of memory CD4(+) lymphocytes and naive CD8(+) lymphocytes was significantly lower in the middle ear effusion. Lymphocyte subsets were compared between 22 pairs of effusions from each patient. The percentage of each type of cell did not differ significantly. Conclusion: The results of this study indicate local regulation of the lymphocyte profile in middle ear effusions and the same phase of immune response in two ears of the same patient.