Objectives: Rheumatoid arthritis (RA) is a chronic inflammatory disease leading to joint destruction. In addition to involvement of the joints, there is growing evidence that inflammatory/autoimmune processes take place in bone marrow, beginning the disease onset. Activated T and B cells accumulate in bone marrow, where also effective antigen presentation takes place. An increased number of activated T cells was observed in RA in comparison to osteoarthritis (OA) bone marrow. In the present study we analyzed the levels of chemokines that may be responsible for accumulation/retention of T-cells in the bone marrow of RA and OA patients.
Material and methods: Bone marrow samples were obtained from RA and OA patients during total hip replacement surgery, and bone marrow plasma was obtained by gradient centrifugation. Levels of the chemokines CX3CL1, CCL5, CCL2, CXCL12 and CXCL1 were measured in bone marrow plasma by specific ELISAs. Comparison between the groups of patients and statistical significance were analyzed by the two-tailed Mann-Whitney U test.
Results: Increased levels of CX3CL1 (818 ±431 pg/ml vs. 502 ±131 pg/ml, p < 0.0007) and CCL5 (5967 ±1680 pg/ml vs. 4878 ±2360 pg/ml, p < 0.05) respectively in bone marrow plasma from RA in comparison with OA patients were observed. In contrast, similar levels of CCL2, CXCL12 and CXCL1 in RA and OA bone marrow suggest that these cytokines do not play a significant role in the observed T cell accumulation in RA bone marrow.
Conclusions: CX3CL1 and CCL5 overproduced in RA bone marrow may contribute to the accumulation of T cells observed in RA bone marrow.