Our previous studies showed that anti-citrate synthase (anti-CS) immunoglobulin (Ig)M natural autoantibodies are present in healthy individuals without previous antigen stimulation, but no studies have investigated their presence in the pericardial fluid (PF). Therefore, we detected the natural anti-CS IgG/M autoantibody levels in plasma and PF of cardiac surgery patients and investigated their relationship with cardiovascular disease-associated bacterial pathogens. PF and blood samples of 22 coronary artery bypass graft (CABG) and 10 aortic valve replacement (AVR) patients were tested for total Ig levels, natural autoantibodies and infection-related antibodies using enzyme-linked immunosorbent assay (ELISA) and Luminex methods. The B cell subsets were measured by flow cytometry. The total Ig subclass levels were four to eight times lower in PF than in plasma, but the natural anti-CS IgM autoantibodies showed a relative increase in PF. The frequency of CD19 B lymphocytes was significantly lower in PF than in blood (P = 0·01), with a significant relative increase of B1 cells (P = 0·005). Mycoplasma pneumoniae antibody-positive patients had significantly higher anti-CS IgM levels. In CABG patients we found a correlation between anti-CS IgG levels and M. pneumoniae, Chlamydia pneumoniae and Borrelia burgdorferi antibody titres. Our results provide the first evidence that natural autoantibodies are present in the PF, and they show a significant correlation with certain anti-bacterial antibody titres in a disease-specific manner.

BACKGROUND: Composition of pericardial fluid (PF) may reveal immunological processes influencing oxidative stress and microcirculation of different tissues of the heart and may play a role in the course of myocardial infarction, atherosclerosis, and aortic stenosis. PATIENTS AND METHODS:We investigated lymphocyte populations, cardiovascular markers and immunoglobulin composition in PF and blood samples of patients undergoing CABG operation and compared them to those who had aortic valve surgery. RESULTS:The amount of CD8 + T, NK, memoT and activated T-cytotoxic cells were elevated in PF compared to blood, but naiveT and activated T-helper cell ratio were lower in PF. Amount of activated T-helper cells and regulatory T-lymphocytes were elevated in CABG participants in both PF and blood. INKT cells represented the only regulatory lymphocyte population reaching significantly higher concentration in PF than in blood. IL-6 and MCP1 level were elevated in PF compared to blood and MCP1 plasma level was markedly elevated in CABG group. CONCLUSIONS: Our study describes a comprehensive immunological analysis of PF in humans for the first time. We showed that the investigated lymphocyte populations and cardiovascular markers in PF have significantly different distribution compared to blood, and lymphocyte populations show different compartmentization in coronary disease and aortic stenosis.

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