Fyn-specific kinase activity is elevated in patients with asymptomatic HIV infection. The study population consists of patients with asymptomatic (Asx) HIV infection (n = 14), symptomatic AIDS (AIDS) (n = 4), normal, HIV-seronegative controls (ctrl) (n = 47), patients with chronic hepatitis B (HepB) infection (n = 6), patients with chronic hepatitis C (HepC) infection (n = 7), normal donors with prior exposure to CMV (n = 7), and patients with systemic lupus erythematosis (SLE, n = 6). PBMC were isolated from whole blood and lysate from 5 × 10⁶ cells immunoprecipitated with antibodies specific to p59^fyn(T). Immune-complex kinase assays, Western immunoblotting of Fyn protein, and calculation of the relative specific kinase activity of Fyn was done as described in Fig 3. The results represent the mean Fyn specific kinase activity ± SEM.