In a mouse model of rheumatoid arthritis (RA) known as KxN,…
In a mouse model of rheumatoid arthritis (RA) known as KxN, mice develop RA beginning at about 4–5 weeks of age. This autoimmune disease symptoms include joint swelling and infiltration of inflammatory cells with eventual deterioration of bone and cartilage. To address whether T cells or B cells were required for autoimmune disease initiation and/or progression, a series of studies were performed. In one study, CD4 T cells were eliminated in young KxN mice by injection of a cell-depleting anti-CD4 antibody (or an isotype control antibody), and disease progression was monitored (graph on the left). In a second study, anti-CD4 antibody was injected into KxN mice after disease symptoms had already appeared. The mice were then monitored for the ensuing several weeks (middle graph). In a third study, KxN mice were crossed to a line of mice with a mutation that blocks all B cell development. KxN B-cell-deficient mice were then compared to KxN B-cell-sufficient mice for the development of RA symptoms (graph on the right). What do these data indicate about the role of T cells and B cells in the development and disease progression of RA in this mouse model? Explain your reasoning using the data above.