The authors were interested in measuring the overall degree of immunosuppression in solid organ transplant recipients (SOTRs)by using a novel global cell-mediated immunity (CMI) assay. They enrolled 137 consecutive SOTRs who provided whole blood to conduct the global CMI assay (QuantiFERON Monitor) at 1, 3 and 6 months posttransplant. The assay measures plasma interferon gamma (IFN-γ) levels following stimulation with antigens that stimulate both innate and adaptive immunity. The median age of participants was 58 years and transplant types were kidney (32.1%), liver (30.7%) and lung (36.5%). At least one episode of infection occurred in 23.4% patients between 1 and 3 months, 25.1% between 3 and 6 months, and 29.5% between 6 and 12 months. IFN-γ levels were found to be significantly lower in those participants with at least one episode of infection vs. no infection at months 1, 3 and 6. Participants who developed opportunistic infections (OIs) also had significantly lower CMI than those without OI at months 3 and 6. When the authors used a cutoff value of ≤10 IU/mL of IFN-γ, there was a two- to threefold greater likelihood of subsequent infection in those with lower CMI. Therefore the use of this global immunity assay enables the quantification of immunosuppression in order to predict the risk of subsequent infection episodes in organ transplant recipients.
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