Attempt to enhance resistance to infection in 6-mercaptopurine treated mice by lysozyme administration and immunization with Escherichia coli O86 antigen.

Long-term immunosuppressive therapy of mice with 6-mercaptopurine (6-MP) for 2 and/or 3 weeks results in partial lethality, decrease of total leukocyte count, of serum lysozyme level and in bacteremia. The adverse effect of 6-MP treatment could not be prevented by lysozyme administration; immunization with Escherichia coli O86 antigen further increased the lethality of 6-MP in mice. The results stress the potential danger of immunization with bacterial antigens during immunosuppressive therapy.