IGHG3 and T-cell acute lymphoblastic leukemia: Human T-ALL is characterized by immune incompetence, abnormal cytokine production and severe hypogammaglobulinemia.2, 3 Serum levels of immunoglobulins in Eμ-HMGA2 transgenic mice were severely decreased relative to those in wild-type littermates (Figure 5a), including IgG1, IgG2a, IgG2b and IgG3.