The pleural space is a potential compartment between the lung and chest wall that becomes filled with fluid and inflammatory cells in a number of respiratory diseases. In an attempt to understand one aspect of the inflammatory process in the pleural space, we compared the responses in three different diseases (congestive heart failure [CHF], tuberculosis [TB], and cancer). Large concentrations of interleukin-8 (IL-8) were detected in cancer and TB effusions, but not in CHF. Surprisingly, the concentration of IL-8 correlated best with lymphocyte recruitment and not with neutrophil recruitment. Pleural fluid from cancer and TB patients was chemotactic for lymphocytes, and this activity was partly blocked by an anti-IL-8 antibody in cancer and completely blocked in TB. To determine whether there was the potential for a chemotactic gradient into the pleural space, pleural effusion cells were analyzed for the expression of IL-8. Cells in the effusions of cancer patients expressed IL-8, whereas IL-8 could not be detected from the cells of TB and CHF effusions. To explore the possible role of pleural macrophages in the regulation of IL-8, pleural effusion cells were treated with culture supernatants from stimulated pleural macrophages. Stimulated pleural macrophages were able to induce expression of messenger RNA (mRNA) for IL-8 and IL-8 protein production, and this activity was abrogated by blocking tumor necrosis factor- α . These findings suggest that soluble IL-8 is an important factor for the recruitment of lymphocytes into the pleural space, and that this cytokine is produced by both pleural structural and cancer cells after their activation by macrophage-derived, cytokine-mediated signals.
Neutrophil infiltration is central to the pathogenesis of Clostridium difficile toxin A-induced enterocolitis. This study examines whether monocyte activation by C. difficile toxins is instrumental in initiating neutrophil activation and recruitment. Human monocytes were exposed to low concentrations of highly purified C. difficile toxins, and the conditioned media were harvested for cytokine and functional assays. Monocytes exposed to C. difficile toxin A (10−10 M) or toxin B (10−12 M) released 100 and 20 times basal levels, respectively, of the neutrophil chemoattractant interleukin-8 (IL-8). Reverse transcriptase-polymerase chain reaction demonstrated a marked increase in IL-8 mRNA expression by monocytes 3 h after toxin exposure. Conditioned media from toxin A- and toxin B-treated monocytes stimulated neutrophil migration (324 and 245% of control, respectively). This effect was completely blocked by IL-8 antiserum. These media also upregulated neutrophil CD11b/CD18 and endothelial cell intercellular adhesion molecule-1 expression. C. difficile toxins, at low concentrations, potently activate monocytes to release factors, including IL-8, that facilitate neutrophil extravasation and tissue infiltration. Our findings indicate a major role for toxin-mediated monocyte and macrophage activation in C. difficile colitis.
Prostaglandin D2 (PGD2) is released following exposure of asthmatics to allergen and acts via the adenylylcyclase–coupled receptor for PGD2 (DP receptor). In this study, it is reported that human eosinophils possess this receptor, which would be expected to inhibit their activation. In contrast, it was found that prostaglandinD2 is a potent stimulator of eosinophil chemotaxis, actin polymerization, CD11b expression, and L-selectin shedding. These responses are specific for eosinophils, as neutrophils display little or no response to prostaglandinD2. They were not due to interaction with receptors for other prostanoids, as prostaglandins E2 and F2a, U46619 (a thromboxane A2 analogue), and carbaprostacyclin (a prostacyclin analogue) displayed little or no activity. Furthermore, they were not shared by the selective DP receptor agonist BW245C and were not prevented by the selective DP receptor antagonist BWA868C, indicating that they were not mediated by DP receptors. In contrast, the prostaglandin D2 metabolite 13,14-dihydro-15-oxoprostaglandin D2 induced eosinophil activation but did not stimulate DP receptor–mediated adenosine 3’,5’–cyclic monophosphate (cAMP) formation. These results indicate that in addition to the classic inhibitory DP1 receptor, eosinophils possess a second, novel DP2 receptor that is associated with PGD2-induced cell activation. These 2 receptors appear to interact to regulate eosinophil responses to PGD2, as blockade of DP1 receptor–mediated cAMP production by BWA868C resulted in enhanced DP2 receptor–mediated stimulation of CD11b expression. The balance between DP1 and DP2 receptors could determine the degree to which prostaglandin D2 can activate eosinophils and may play a role in eosinophil recruitment in asthma.
link to pdf at bloodjournal.hematologylibrary.org/content/98/6/1942.full.pdf
Chemotaxis has been studied by classical methods that measure chemotactic and random motility responses in vitro, but these methods do not evaluate the total number and phenotype of migrating leukocytes simultaneously. Our objective was to develop and validate a novel assay, combined Boyden-flow cytometry chemotaxis assay (CBFCA), for simultaneous quantification and phenotypification of migrating leukocytes. CBFCA exhibited several important advantages in comparison to the classic Boyden chemotaxis assay (CBCA): 1) improved precision (intra-assay coefficients of variation (CVs): CBFCA-4.7 and 4.8% vs. CBCA-30.1 and 17.3%; inter-observer CVs: CBFCA-3.6% vs. CBCA 30.1%); 2) increased recovery of cells, which increased assay to provide increased sensitivity; 3) high specificity for determining the phenotype of migrating/attracted leukocytes; and 4) reduced performance time (CBFCA 120 min vs. CBCA 265 min). Other advantages of CBFCA are: 5) robustness, 6) linearity, 7) eliminated requirement for albumin and, importantly, 8) enabled recovery of migrating leukocytes for subsequent studies. This latter feature is of great benefit in the study of migrating leukocyte subsets. We conclude that the CBFCA is a novel and improved technique for experiments focused on understanding leukocyte trafficking during the inflammatory response.