We describe a patient with transient disappearance of B-cells, hypogammaglobulinemia, and mild pancytopenia after acute hepatitis. Both HLA-DR+CD8+ and intracellular interferon-gamma+/interleukin-4- cell levels were markedly increased, resulting in an increase in the cytotoxic T-cell (T(C))1/Tc2 and helper T-cell (T(H))1/T(H)2 ratios. After immunosuppressive therapy with cyclosporine A, these parameters of T-cell activation were clearly decreased, and hematologic recovery, including an increase in B-lymphocytes and immunoglobulin concentration, was obtained. These results suggest that there had been suppression of B-cells by activated T-cells. Some patients with common variable immunodeficiency show similar activation of T-cell function, and the present findings suggest the possibility of immunosuppressive therapy for such patients.