An increased frequency of severe infectious diseases in ABOi recipients (doubled versus ABOc within 2 years, P = 0.042) coincided with profoundly downregulated peripheral blood B cell subsets for at least 2 years, impaired in-vitro B cell responses (T-dependent: 2 years, versus ABOc: P = 0.004) and significantly lower CD4+ and CD8+ T cell counts (versus ABOc; 6 months, P = 0.046 and 3 months, P = 0.011, respectively). The gene discussed is CD4; the disease is infectious disease.