EFNB1 and EFNB2 are ligands for Eph receptor tyrosine kinases. This study was undertaken to investigate how the expression of Efnb1 and Efnb2 on murine T cells influences the pathogenesis of collagen-induced arthritis (CIA) and to assess correlations between the T cell expression of these 2 molecules and measures of disease activity in patients with rheumatoid arthritis (RA).
CIA was studied in mice with T cell-specific deletion (double gene knockout [dKO]) of both Efnb1 and Efnb2. Expression of EFNB1 and EFNB2 messenger RNA (mRNA) in peripheral blood T cells from patients with RA was determined by quantitative reverse transcription- polymerase chain reaction.
In dKO mice, clinical scores of arthritis were reduced compared to those in wild-type (WT) control mice. Serum collagen-specific antibody titers in dKO mice were lower than those in WT mice. In analyses based on equal cell numbers, dKO mouse T cells, as compared to WT mouse T cells, provided vastly inferior help to B cells in the production of collagen-specific antibodies in vitro. T cells from dKO mice were compromised in their ability to migrate to the arthritic paws in vivo and in their ability to undergo chemotaxis toward CXCL12 in vitro. Deletion mutation of Efnb1 and Efnb2 intracellular tails revealed critical regions in controlling T cell chemotaxis. T cells from RA patients expressed higher EFNB1 mRNA levels, which correlated with RA symptoms and laboratory findings.
Efnb1 and Efnb2 in T cells are essential for pathogenic antibody production and for T cell migration to the inflamed paws in mice with CIA. These findings suggest that the expression of EFNB1 in T cells might be a useful parameter for monitoring RA disease activity and treatment responses.