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Background Studies conducted in farm environments suggest that diverse microbial exposure promotes children's lung health. The underlying mechanisms are unclear, and the development of asthma-preventive strategies has been delayed. More comprehensive investigation of the environment-induced immunoregulation is required for better understanding of asthma pathogenesis and prevention. Exposure to air pollution, including particulate matter (PM), is a risk factor for asthma, thus providing an excellent counterpoint for the farm-effect research. Lack of comparable data, however, complicates interpretation of the existing information. We aimed to explore the immunoregulatory effects of cattle farm dust (protective, Finland) and urban air PM (high-risk, China) for the first time using identical research methods. Methods We stimulated PBMCs of 4-year-old children (N = 18) with farm dust and size-segregated PM and assessed the expression of immune receptors CD80 and ILT4 on dendritic cells and monocytes as well as cytokine production of PBMCs. Environmental samples were analysed for their composition. Results Farm dust increased the percentage of cells expressing CD80 and the cytokine production of children's immune cells, whereas PM inhibited the expression of important receptors and the production of soluble mediators. Although PM samples induced parallel immune reactions, the size-fraction determined the strength of the effects. Conclusions Our study demonstrates the significance of using the same research framework when disentangling shared and distinctive immune pathways operating in different environments. Observed stimulatory effects of farm dust and inhibitory effects of PM could shape responses towards respiratory pathogens and allergens, and partly explain differences in asthma prevalence between studied environments.

Exposure to farm environment has been shown to both protect from allergic diseases and increase the risk of respiratory syndromes. Mechanisms have been previously investigated by using farm dust extracts or specific components of dust. The use of authentic farm dust would better reflect the natural exposure. The aim of our study was to highlight the importance of proper assessment of the cow stable dust characteristics before conducting further investigations. For this purpose, we characterized microbiome and size distribution of unprocessed cow stable dust and its toxicological properties, as they have been often overlooked in search of protective factors. Stable dust samples from four Finnish dairy farms were collected by utilizing two different collection methods. Toxicological potential was analysed by stimulating co-cultures of lung epithelial and macrophage-like cells with dust. Size and mass distributions of airborne particles in the stables and bacterial and fungal microbiota of the dust were analysed. Stimulation with dust did not affect viability, but heightened oxidative stress responses and cytokine secretion, and slightly reduced the metabolic activity. There were a few differences in responses between farms, however, the differences were mainly in the intensity and not in the direction of the response. Cellular responses induced by dusts collected by different sampling methods did not differ substantially. Unprocessed stable dust samples showed relatively low direct toxicity but were able to trigger immune responses in studied cell model. This suggest that these dust collection methods could be utilized when investigating e.g. asthma-protective mechanisms.

The effect of cryopreservation on antigen-presenting cells (APCs) is understudied. It is important to understand the effects of cryopreservation on these cells as they play a major role in immune responses, and they could be utilized in different clinical applications. In this study, we compared fresh and cryopreserved PBMCs in regards of their general immune responsiveness and, furthermore, the effect of cryopreservation on the circulating APCs among PBMCs. We stimulated fresh and cryopreserved PBMCs (N = 6) with LPS or Poly(I:C).Cytokine production of PBMCs and expression of functional markers CD80 and ILT4 on major types of APCs, dendritic cells (DCs) and monocytes, were analysed. We also analysed whether cryopreservation affects different subtypes of DCs (plasmacytoid and myeloid DCs) differently. Cryopreserved PBMCs produced less cytokines than fresh cells in response to stimulation, but the response profiles were comparable. Cryopreservation had also an effect on the relative proportions of APCs. Stimuli-induced responses were somewhat parallel but weaker than those observed in fresh cells. This study suggests that the use of cryopreserved cells is more suitable in studies that assess general responses to stimuli instead of measuring exact levels of reactions. Thus, the interpretation and comparison of the results of different studies should not be done without considering the differences in cryopreservation techniques and their effects on PBMCs and, more specifically, on APCs.

PROBLEM Birth-related factors and neonatal treatments could affect the maturation of immune system and thus have lasting effects on immune responses. We investigated the effect of obstetric factors other than being born by cesarean section on immune responses later in life. METHOD OF STUDY Regulatory, inflammatory, TH1 and TH2 cytokines, and a chemokine were analyzed in unstimulated and Toll-like receptors (TLRs) 2-, 3-, and 4-stimulated PBMCs of teenagers born by cesarean delivery (CD; N=79). Data on obstetric factors were collected from patient data archives. RESULTS Advanced cervical dilatation at the time of CD associated with higher unstimulated production of cytokines compared to adolescents who were delivered before the onset of labor. Neonatal intensive care treatment associated with lower unstimulated production of cytokines. Similar associations were found following TLR stimulations. CONCLUSION The lack of natural processes of delivery and neonatal intensive care treatment might lead to long-lasting impairment of immune responses.