Objective: To determine if sustained immunologic effects occurred after treatment of patients with rheumatoid arthritis (RA) with an immunoconjugate of murine anti-CD5 monoclonal antibody with ricin A chain (anti-CD5).
Methods: We measured lymphocyte populations, mitogen induced peripheral blood mononuclear cell (PBMC) stimulation, cytokine levels, immunoglobulin levels, in vivo immune function, and clinical outcomes in 9 patients with RA treated with anti-CD5.
Results: The treatment of patients with RA with anti-CD5 was associated with marked acute depletion of peripheral blood lymphocytes (p < 0.01) during and immediately after treatment. A sustained decrease in the number of CD3, CD4, CD5, and CD8 bearing lymphocytes persisted for 2 months after treatment (p < 0.05). After 3 months a mild decrease in the number of these lymphocyte populations persisted, but when compared to baseline values, the differences were not found to be statistically significant. Phytohemagglutinin induced PBMC proliferation was decreased at the 3-month followup (p < 0.05). Evaluations of mitogen induced cytokine and immunoglobulin production, immunoglobulin level, autoantibody, and in vivo antibody response to tetanus toxoid did not show any consistent change from baseline.
Conclusion: Anti-CD5 treatment of RA appears to be associated with a decrease in the population of cells bearing CD5, but does not appear to induce any persistent immunologic abnormalities.