The Effect of Lymph Isolated during Osteopathic Lymphatic Pump Treatment on the Immune Response against Acute Pneumonia
Purpose: Community acquired pneumonia (CAP) accounts for over 1,000,000 hospital admissions yearly. Osteopathic physicians use lymphatic pump techniques (LPT) as a tool to mobilize lymph and treat infectious disease, such as CAP. Recent research supports LPT as an adjunctive therapy in the treatment of CAP, such as streptococcal pneumonia; however, the exact mechanism by which LPT is protective in this setting is unknown. As the first line of defense, resident alveolar macrophages respond to pathogens by engulfing bacteria and secreting antimicrobials such as nitric oxide and inflammatory mediators such as TNF-α. Thus, alveolar macrophages are key regulators in the immune response to airway pathogens. The overall objective of this study is to identify the biological effect of the thoracic duct lymph (TDL) mobilized during LPT on the immune response against streptococcal pneumonia. In this study, we hypothesized that lymph mobilized during LPT would suppress the inflammatory effect of alveolar macrophages against lipoteichoic acid (LTA), a component of the cell wall of S. pneumoniae. Methods: To test our hypothesis, TDL was collected from 6 mongrel dogs during 4 minutes of baseline (baseline TDL), during 4 minutes of LPT (LPT TDL), and during 10 minutes following LPT (post-LPT TDL). The murine alveolar macrophage cell line, MH-S, was cultured in media or media plus 5% phosphate buffer saline (PBS), 5% baseline TDL, 5% LPT TDL, or 5% post-LPT TDL and co-cultured with or without LTA. After 24 hours of culture, the supernatant was collected to measure the production of nitrite and TNF-α. Alveolar macrophage viability was measured by flow cytometry using the markers annexin V and propidium iodide. Results: Alveolar macrophages did not produce nitrite or TNF-a in the absence of stimulation with LTA. During culture with LTA, the addition of baseline, LPT, or post-LPT TDL significantly (P0.05). Furthermore, there were no differences in TNF-α and IL-10 production by MH-S macrophages cultured with baseline, LPT, or post-LPT TDL with or without LTA. Conclusions: In vitro, TDL reduced some of the inflammatory activity of macrophages that are associated with the immune pathology caused by S. pneumoniae. By mobilizing lymph into circulation, LPT may mobilize protective factors to the lung to reduce inflammation, thereby protecting from pulmonary disease. A better understanding of the physiological effects of LPT will allow us to expand translational and clinical research and guide osteopathic practitioners in their clinical practice.