Higher frequencies of CMV-specific CD4⁺ T cells are present in patients with B-CLL. CMV-specific CD4⁺ responses were assessed using CFC following stimulation of whole blood using CMV lysate. CMV-specific T cells were determined by production of intracellular (A) IFNγ, (B) TNFα, or (C) IL-2. A higher frequency and absolute number of CMV-specific CD4⁺ T cells were present in CMV-seropositive patients relative to the age-matched CMV-seropositive control group (n = 35).