Training modifies innate immune responses in blood monocytes and in pulmonary alveolar macrophages.

This study showcases how physical training, not just strenuous exercise, affects the innate immune responses in two different compartments of humans and horses – the blood monocytes and pulmonary alveolar macrophages (PAMs). Notably, it was observed that training affects the expression of toll-like receptors (TLRs) which play key roles in lung defense mechanisms, ultimately modifying susceptibility to respiratory infections.

Methodology and Data Collection

• The researchers collected blood monocytes and pulmonary alveolar macrophages (PAMs) from untrained, moderately trained, intensively trained, and deconditioned horses before and after a strenuous exercise test. This was done to examine the effect of varying stages of physical conditioning on innate immune responses.
• TLR mRNA expression was analyzed in vitro using real-time PCR to measure the alterations in expression that occurred due to training.
• Cytokine production, an important factor in inflammatory and immune responses, was observed after in vitro stimulation with TLR ligands, a process which is measured through ELISA (Enzyme-Linked Immunosorbent Assay).

Discussion of the Results

• The results demonstrated that training, as opposed to acute exercise, modified the innate immune responses in both cell types.
• Training down-regulated the mRNA expression of TLR3 in both cell types while up-regulating the expression of TLR4 in monocytes, implying an alteration in the immune response due to physical conditioning.
• Increased cytokine secretion was observed in trained and deconditioned subjects once monocytes were treated with LPS (a bacterial endotoxin) and a synthetic diacylated lipoprotein. This suggests a heightened activation of cells at the systemic level in response to these treatments.
• The production of TNF-α (tumor necrosis factor alpha) and IFN-β (interferon beta), which plays crucial roles in the immune response, decreased in non-stimulated and stimulated PAMs in trained and deconditioned horses.
• The observed decrease in the production of these immune response regulators could explain the increased susceptibility to respiratory infections, linking physical training with immune response alteration.

Conclusion of the Study

• This research provides evidence of a dissociation between the systemic level and lung response to training and physical conditioning.
• Such dissociation is likely implicated in systemic inflammation as well as an increased susceptibility to pulmonary infections, providing a link between physical exercise, training, and immune response.