Streptococcal cell wall induced arthritis: leukocyte activation in extra-articular lymphoid tissue

Rheumatoid arthritis (RA) is a common systemic inflammatory disease thought to be T-helper-1 cell driven, though current controversy involves the relative role of T cells versus other leukocytes. Thus, there is a need for better understanding of the role of various leukocytes and their subsets in RA. Using the streptococcal cell wall (SCW) induced arthritis model, we examined leukocytes isolated from peripheral blood, spleen, and lymph nodes using monoclonal antibodies directed against lineage specific cell surface markers. Activation status of these cells was assessed using CD44 and CD71 as markers. T cells in general, and CD4+ T cells in particular were found to be activated in spleen and lymph nodes. B cells and monocytes in spleen demonstrated increased activation as well. The activation of cells in the myeloid and lymphoid lineages in the chronic phase of arthritis indicates ongoing involvement of innate and cognate immunity. This study quantitates specific changes in B and T lymphocytes, and myeloid cells and is consistent with findings in human RA in which specific antibodies, T cells, and myeloid cells are all implicated in the pathogenesis of RA.