Therapeutic opportunities in fibroblasts in inflammatory arthritis.

The Identification of key players of inflammation and pathologic immune response in rheumatoid arthritis (RA) has resulted in the development of novel therapeutic strategies revolutionising the treatment of disease. However, these new therapeutics only indirectly affect the mesenchymal compartment of the inflamed synovium and, in particular, the specific phenotype of activated fibroblast-like cells. These cells have been demonstrated to trigger not only the progressive destruction of articular cartilage and bone but also the switch from acute to chronic inflammation.

CD4+ T cells control the differentiation of Gr1+ monocytes into fibrocytes.

Fibrocytes are collagen-type-I-producing cells that arise at low frequency from hematopoietic cells. We have analyzed in mice which leukocyte subsets are required for generation of fibrocytes and show that murine fibrocytes develop from the subpopulation of CD11b(+) CD115(+) Gr1(+) monocytes under the control of CD4(+) T cells. In the absence of CD4(+) T cells, differentiation of fibrocytes was markedly reduced in vitro and in vivo.

Important role of interleukin-3 in the early phase of collagen-induced arthritis.

Objective: Activation of basophils contributes to memory immune responses and results in exacerbation of collagen-induced arthritis (CIA). We undertook the present study to analyze the production and biologic effects of interleukin-3 (IL-3), a strong activator of basophils, in CIA.

Methods: Arthritis was induced by immunization with type II collagen.

Basophils enhance immunological memory responses.

The cellular basis of immunological memory remains a controversial issue. Here we show that basophils bound large amounts of intact antigens on their surface and were the main source of interleukins 6 and 4 in the spleen and bone marrow after restimulation with a soluble antigen. Depletion of basophils resulted in a much lower humoral memory response and greater susceptibility of immunized mice to sepsis induced by Streptococcus pneumoniae.

Targeting of Gr-1+,CCR2+ monocytes in collagen-induced arthritis.

Objective: The chemokine receptor CCR2 is highly expressed on monocytes and considered a promising target for treatment of rheumatoid arthritis. However, blockade of CCR2 with a monoclonal antibody (mAb) during progression of collagen-induced arthritis results in a massive aggravation of the disease. In this study we investigated why CCR2 antibodies have proinflammatory effects, how these effects can be avoided, and whether CCR2+ monocytes are useful targets in the treatment of arthritis.