MKI67 and Opportunistic infection: If defective molecules involving activation pathways inhibit [3H]-thymidine nucleotide incorporation, incremental CFSE dilution, and nuclear Ki-67 entrance, the quantitative value of [3H]-thymidine measured using a beta-counter and flowcytometric percentages of CFSE and Ki-67 will increase less during stimulation, and this can explain recurrent opportunistic infections.