Immunology of lymphocytes in pleural reactions

The immunocompetence of lymphocytes in pleural fluid may be different than the peripheral blood. 60-200 ml of pleural fluid (PF) was obtained by thoracentesis from 10 patients. The specimens were collected in sterile containers with 1000 units of heparin/100 ml PF. Venous blood (VB) was obtained in a similar manner from 6 of the 10 patients within 24 hours of each thoracentesis. The PF's and VB's were analyzed within 2 hours of the thoracentesis. Thymus derived lymphpocytes (T cells) by rosette formation with sleep RBC, the proliferative response to antigen or mitogen, burse equivalent lymphocytes (B cells) by surface immunoglobulins were assayed. There was a wide range of total PF cells (600-41,200 cells/mm³) with the lymphocytes also varying from 6-100%. The mean of T cells was 62% ± 5.4 SEM in the PF and 67% ± 4.8 in VB. For B cells the mean was 27% ± 3.9 in the PF and 29% ± 4.6 in VB. Lymphocytes bearing neither T cell nor B cell markers did not exceed 10%. PF lymphocytes in all patients were stimulated by phytohemagglutinin (PHA). Stimulation Index (SI) was 3-69. The SI is defined by counts/minute in culture with antigen or mitogen divided by counts/minute without antigen or mitogen. Several trends were discovered in the following pleural diseases. In 2 of 3 patients with pneumonia and effusion there were decreased percentages of PF T cells (30,44) suggesting increased B cell response to the bacterial infection. In 2 patients with tuberculous pleurisy there was a striking ability of the PF lymphocytes to be stimulated by PPD (PF SI=24,25; VB SI=3,3). In 1 patient with adenocarcinoma of the lung metastatic to the pleura there was greater PF lymphocyte reactivity to PHA (PF SI=43; VB SI=1) and PPD (PF SI=23; VB SI=1). The PF lymphocyte is a viable part of the immune system with subpopulations of T and B cells similar to VB. PF T cells respond to mitogen and antigen stimulation. The PF lymphocyte has properties of an immunocompetent cell and in some cases may be more active than the VB lymphocyte.