Effects of climatic environment on the immunological features of rheumatoid arthritis

In this study, we aimed to comprehensively assess the percentages of CD4+ T-cell and B-cell subpopulations in peripheral blood collected from HC and RA patients and compare them between the two locations. The altitude difference between Tsukuba City and Karuizawa Town is as much as 1000m, and the difference in average temperature and atmospheric pressure is large. Therefore, studying populations from these two locations can elucidate the effects of climate on the immunological signature of RA. To control for potential confounders such as age, sex, RF and anti-CCP antibody positivity, prednisolone dose, methotrexate dose, bDMARD or tsDMARD use, and DAS28-CRP in the RA cohort, propensity scores IPW adjustment was adopted. , age and gender of the HC cohort from Tsukuba to Karuizawa. Our analysis revealed that the proportions of T and B cell subpopulations differed significantly not only in RA patients but also in HC between Tsukuba and Karuizawa, irrespective of background characteristics such as the presence or absence of RA. , suggested that climate change could intrinsically affect immune cell phenotypes. Furthermore, some of the differences in T and B cell subpopulations were only observed in RA patients, suggesting that RA indicating that it may be a characteristic immunophenotype.

In T-cell subpopulations, there was a significant increase in cTh1, cTfh1, and Tph cells, and cTh17, cTh17.1, and CD8+ Treg cells in Karuizawa RA patients compared with Tsukuba RA patients after IPW. A significant decrease in was observed. adjustment. Among these T cell subpopulations, Tph cells tended to increase, and cTh17 and CD8+ Treg cells were significantly increased in RA patients compared with Karuizawa HC. However, there was no significant correlation between T-cell subpopulations, which were significantly different between Tsukuba and Karuizawa, and RA disease activity. IFNγ-secreting Th1 cells were identified in synovial fluid of RA patients^9,Tenand induces macrophage activation characterized by an increased ability to produce pro-inflammatory cytokines such as TNF¹¹a previous study reported that there was no significant difference in peripheral blood CXCR3+CCR6− Tfh1 cells between RA patients and HC¹²Tph cells are defined as PD-1^HiCXCR5^–CD4⁺ Reportedly poised to promote T cells, and B cell responses and antibody production within the pathologically inflamed non-lymphoid tissues of RA¹³Combining mass cytometry and transcriptomics also revealed expansion of Tph cells in the RA synovium¹⁴Our previous studies and other reports indicate a pathogenic role of Th17 cells in RA^15,16,17Th17.1 cells, a subgroup of Th17 cells characterized by expression of CXCR3 and production of IFNγ, are the most pathogenic among Th17 cells and have been reported as predictors of therapeutic response in RA patients. .^18,19.CD122⁺CD8⁺Treg cells have the ability to inhibit T cell responses and suppress autoimmunity, but their role in RA remains unclear.²⁰Therefore, it has been speculated that the climatic environment may influence the pathology of RA through the alternation of T cell subpopulations.

Analysis of B cell subpopulations showed that DNB cells, DN1 B cells, DN2 B cells, and class-switched memory B cells increased significantly after IPW adjustment, while unswitched memory B cells, naive B cells, and ABC increased significantly. showed a significant decrease. His RA patients in Karuizawa and those in Tsukuba were compared. Among these B-cell subpopulations, unswitched memory B cells were significantly decreased, whereas ABC was significantly increased in RA patients compared with Karuizawa HC. However, there was no significant correlation between the B-cell subpopulations, which were significantly different between Tsukuba and Karuizawa, and RA disease activity. DNB cells are defined as IgD-CD27-B cells and depending on the expression of CXCR5 he is classified as DN1 or DN2 cells. DNB cells are of interest in the field of autoimmunity, especially in systemic lupus erythematosus (SLE). Autoreactive DN2 B cells proliferated and differentiated into autoantibody-secreting plasmablasts via hypersensitivity to extrafollicular Toll-like receptor 7.^{twenty one}Regarding RA, several studies have reported that DNB cells were increased in RA, especially in ACPA+ patients.^{twenty two,twenty three}On the other hand, immunoglobulin class switching and further differentiation of memory B cells are mediated by TB interactions at germinal centers, and enhancement of this process was suggested by two findings. – Switch memory B cells^{twenty four} Second, subjects carrying the RA-associated risk haplotype B lymphoid kinase (BLK), a member of the Src family of tyrosine kinases, had significantly increased numbers of class-switched memory B cells. .^{twenty five,26}ABC is a newly identified B-cell subset found to accumulate in the spleens of aged mice and model mice of systemic lupus erythematosus.^27,28Furthermore, expansion of human ABC has been observed in many autoimmune diseases, including RA.²⁹Therefore, it was speculated that the climatic environment may also influence the pathogenesis of RA through the alternation of B cell subpopulations.

Our analysis revealed that the proportions of T-cell and B-cell subpopulations were significantly altered when comparing the Tsukuba and Karuizawa populations, but how these cells were altered Whether they interact and modulate RA pathology is unknown. As described above, Tph cells have been reported to play an important role in promoting B cell responses and antibody production.^13,14and DNB cells and class-switched memory B cells are also associated with autoantibody formation, including ACPA formation in RA^{twenty two,twenty three,twenty four}Consequently, the increase in Tph cells, DNB cells, and class-switched memory B cells in the Karuizawa population raises the possibility that enhanced autoantibody production is one of the mechanisms underlying RA associated with the climatic environment. .

Questions remain about how climatic factors such as temperature and pressure regulate immune cell differentiation and function in RA. Significant relationships have been reported for her CD4+, CD8+ T-cell, CD20+ B-cell numbers and percentages, ambient temperature, daylight duration, and air pressure in healthy volunteers.³⁰The systematic effect of general cooling by exposure to cold air at a temperature of -25°C for 5 minutes in healthy volunteers led to a decrease in the number of T lymphocytes in the venous blood, indicating dysfunction.³¹Although environmental factors such as oxygen concentration have been reported,^32,33acidification^34,35salinity³⁶and glucose, amino acid, and lipid metabolism^37,38,39 Although it has altered immune cell differentiation and function and contributed to the pathogenesis of autoimmune diseases, how climatic factors such as temperature and atmospheric pressure modulate immune cell function and the development of autoimmune diseases, including RA, remains unclear. remains unknown.

The current study has some limitations. First, it was speculated that temperature had little effect on the study results, as the average Japanese living environment has almost perfect temperature control. Second, patients recruited for this study from both Tsukuba and Karuizawa were well treated and their RA was well controlled with antirheumatic therapy, including b/tsDMARDs. Indeed, our results in HC revealed that differences in the percentage of peripheral blood immune cells appeared to be more pronounced and were observed in more T and B cell subpopulations than in RA patients. Third, as mentioned above, we were unable to clarify how the climatic environment modulates immune cell function and pathology. Fourth, all blood samples had to be frozen for storage. Also, the samples from Karuizawa had to be transported to Tsukuba and analyzed there. FACS results were not statistical but differed slightly in some immune cell subsets such as cTh17, cTfh17, and Breg cells (Supplement Fig. 3 When Four), there was a difference between the presence and absence of cryopreservation, and it seemed difficult to completely eliminate the possibility that cryopreservation and transportation might affect the results. Further studies involving more patients with high disease activity or no therapeutic intervention are needed to elucidate the precise and specific mechanisms of how the climatic environment affects the immune cell-mediated pathology of RA. Is required.

In conclusion, our results suggest that the climatic environment, such as temperature and atmospheric pressure, influences the proportions of T- and B-cell subpopulations and their function, leading to the development of RA, including autoantibody formation, induced by tuberculosis interactions. suggesting that it may be mechanistically related. .