Therapeutic trials in rheumatoid arthritis with the monoclonal antibody Campath-1H have demonstrated recurrent clinical synovitis in some patients, despite profound depletion of circulating lymphocytes. This study was undertaken to examine the cellular infiltrates in synovial tissue at a time of persistent peripheral lymphopenia.
Immunohistochemical staining of synovial tissue and peripheral blood lymphocyte phenotyping.
Synovial tissues from 2 patients with recurrent synovitis after Campath-1H therapy contained significant T lymphocytic infiltrates at a time when circulating T lymphocytes were markedly depleted.
These results demonstrate that peripheral blood analysis may not accurately reflect the synovial tissue response to monoclonal antibody therapy.