Chronic lymphocytic leukemia and autoimmunity: a systematic review

Abstract

Chronic lymphocytic leukemia is frequently associated with immune disturbances. The relationship between chronic lymphocytic leukemia and autoimmune cytopenias, particularly autoimmune hemolytic anemia and immune thrombocytopenia, is well established. The responsible mechanisms, particularly the role of leukemic cells in orchestrating the production of polyclonal autoantibodies, are increasingly well understood. Recent studies show that autoimmune cytopenia is not necessarily associated with poor prognosis. On the contrary, patients with anemia or thrombocytopenia due to immune mechanisms have a better outcome than those in whom these features are due to bone marrow infiltration by the disease. Moreover, fears about the risk of autoimmune hemolysis following single agent fludarabine may no longer be appropriate in the age of chemo-immunotherapy regimens. However, treatment of patients with active hemolysis may pose important problems needing an individualized and clinically sound approach. The concept that autoimmune cytopenia may precede the leukemia should be revisited in the light of recent data showing that autoimmune cytopenia may be observed in monoclonal B-cell lymphocytosis, a condition that can only be detected by using sensitive flow cytometry techniques. On the other hand, there is no evidence of an increased risk of non-hemic autoimmune disorders in chronic lymphocytic leukemia. Likewise, there is no epidemiological proof of an increased risk of chronic lymphocytic leukemia in patients with non-hemic autoimmunity. Finally, since immune disorders are an important part of chronic lymphocytic leukemia, studies aimed at revealing the mechanisms linking the neoplastic and the immune components of the disease should help our understanding of this form of leukemia.

Figure 1.

Mechanisms of autoimmune disease in CLL. (A) CLL cells may process red blood cell antigens and act as antigen presenting cells, inducing a T-cell response and the formation of polyclonal antibodies by normal B cells, thus indirectly provoking autoimmune hemolytic anemia. (B) CLL cells express inhibitory cytokines that alter tolerance, which may facilitate the escape of self-reactive cells. (C) Rarely CLL cells are effector cells that secrete a pathological monoclonal autoantibody. Two such diseases are paraneoplastic pemphigus, where immunoglobulins are cross-reactive with epitopes located at the dermal-epidermal junction, and cold agglutinin disease, where IgMs have anti-red cell reactivity. (D) In turn, CLL cells may be stimulated through their polyreactive BCR that recognizes auto-antigens.