Mechanisms of T-lymphocyte accumulation during experimental pleural infection induced by Mycobacterium bovis BCG.

Tuberculous pleurisy is a frequent extrapulmonary manifestation characterized by accumulation of fluid and inflammatory cells in the pleural space. Here, we investigated the mechanisms of T-lymphocyte accumulation in the pleural space by using a murine model of pleurisy induced by Mycobacterium bovis BCG. Intrathoracic (i.t.) injection of BCG (4.5 x 10(5) bacteria/cavity) induced accumulation of T lymphocytes in the pleural cavities of C57BL/6 mice. We observed the presence of CFU in pleural washes conducted 1, 2, 3, 7, and 15 days after pleurisy induction. Pretreatment with fucoidan inhibited T-lymphocyte accumulation at 1 day, but not at 15 days, after BCG-induced pleurisy. Accordingly, adoptive transfer of fluorescein isothiocyanate-labeled blood mononuclear cells to infected mice showed that T lymphocytes migrated into the pleural cavity 1 day (but not 15 days) after BCG injection. Cell-free pleural wash fluids recovered from mice 1 day after BCG i.t. stimulation (day 1 BCG-PW), but not day 7 or day 15 BCG-PW, induced in vitro T-cell transmigration, which was dependent on L-, P-, and E-selectins. In contrast, day 7 BCG-PW (but not day 1 BCG-PW) induced in vitro T-lymphocyte proliferation via interleukin-2 (IL-2) and gamma interferon (IFN-gamma). Accordingly, in vivo IL-2 or IFN-gamma neutralization abolished T-lymphocyte accumulation 7 days after pleurisy induction. Our results demonstrate that pleural infection induced by BCG leads to T-lymphocyte accumulation in two waves. The acute phase depends on selectin-mediated migration, while the second wave of T-lymphocyte accumulation seems to depend on a local proliferation induced by cytokines produced in situ.

Requirement of L-selectin for gammadelta T lymphocyte activation and migration during allergic pleurisy: co-relation with eosinophil accumulation.

Intra-thoracic antigenic challenge (ovalbumin, 12.5 microg/cavity) led to increased numbers of gammadelta T lymphocytes in pleural cavities, blood and thoracic lymph nodes in sensitized mice within 48 h. Part of these cells expressed CD62L, which increased on gammadelta T cell surfaces obtained from lymph nodes after ovalbumin (OVA) challenge. Selectin blockade by fucoidan pre-treatment (10 mg/kg, i.v.) impaired in vivo increase in CD25(+) and c-fos(+) gammadelta T cell numbers in lymph nodes, indicating a role for selectins on gammadelta T lymphocyte activation and proliferation. In vivo selectin blockade by fucoidan or alpha-CD62L mAb (200 microg/mice, i.p.) also inhibited OVA-induced gammadelta T cell accumulation in pleural cavities. Confirming the direct effect of CD62L on gammadelta T cell transmigration, the migration of i.v. adoptively-transferred CFSE-labeled gammadelta T lymphocytes into pleural cavities of challenged recipient mice was impaired by fucoidan ex vivo treatment. It is noteworthy that eosinophil influx was also impaired in those mice, indicating that reduced eosinophil migration by CD62L in vivo blockade depended on gammadelta T cell migration via CD62L molecules. Accordingly, pleural gammadelta T lymphocytes from fucoidan-treated mice presented reduced OVA-induced IL-5 and CCL11 production. Supporting these data, the depletion of Vgamma4 T lymphocytes, which are pulmonary gammadelta T cells, decreased OVA-induced eosinophil influx into allergic site. Such results demonstrate that CD62L is crucial for the activation of gammadelta T cells in lymph nodes, for their migration into inflamed tissue and for the modulation of eosinophil influx during allergic response.