Serum thymidine kinase, CMV‐specific antibodies and total immunoglobulins in renal transplant patients during immunosuppression with cyclosporine A

The levels of serum thymidine kinase (S‐TK), total IgG, and IgG‐ and IgM‐type antibodies towards cytomegalovirus (CMV) were regularly monitored before and up to half a year post‐transplantation in 24 renal allograft recipients treated with cyclosporine A plus prednisolone. The CMV serology showed that 6 patients had primary infection, while at least 13 had reactivation of the virus. Only 2 patients, one of whom had recurrent infection, had clinical CMV disease. Elevated S‐TK levels up to 150 units were found to precede the increase in anti‐CMV IgG. With 2 exceptions, anti‐CMV IgM was found only in the patients with primary infection. The S‐TK peak related to the increase in anti‐CMV IgG occurred in the majority of the patients with recurrent infection during the first 2 weeks, while 2 of the patients with primary infection had their major S‐TK activity between day 30–60. Additional smaller S‐TK increases were registered after administration of corticosteroids because of rejection. As low S‐TK levels were mostly found before the corticosteroid administration, it was concluded that rejection per sedoes not induce high S‐TK levels. High persistent S‐TK levels were seen only in the patients with overt CMV disease. Scrum total IgG showed huge increases mainly in patients with primary CMV infection. These increases were polyclonal, and significant increases in antibodies to multiple microbial antigens were more prevalent among patients with high increases in the total IgG level. Cytotoxic antibodies to donor lymphocytes were, however, not detected. It is concluded that S‐TK is a useful marker for monitoring CMV disease. The implication of the polyclonal Ig induction on the use of serological tests as well as the possible mechanism of its induction are discussed.