Common chronic lymphatic leukemia antigen (cCLLa); distribution, fate and clinical applications.

The cCLLa is a gp69 antigen expressed by monoclonal cells in patients with CLL, PLL and HCL but not by their normal counterpart or by normal lymphoid or hematopoietic cells nor by other malignant cells. The membrane borne cCLLa sheds spontaneously resulting in serum titers directly proportional to the size of the malignant clone. Both, size of the cCLLa-positive clone and serum cCLLa titers increase with progressing disease. This enables both, the immunophenotypic diagnosis of clinical and preclinical CLL using specific MoAbs, and assessment of the tumor burden. In the presence of specific MoAbs, the cCLLa modulates via internalization. This antigenic behavior, the cytolytic activity of at least one anti-cCLLa MoAb and the expression selectivity of the cCLLa suggest this to be a promising system for exploring immunotherapy of CLL using anti-cCLLa MoAbs or their cytolytic derivatives.