Production of anti-erythrocyte antibodies by leukemic and nonleukemic B cells in chronic lymphocytic leukemia patients

Antibodies Produced by CLL Phenotype B Cells in Patients With Myasthenia Gravis Are Not Directed Against Neuromuscular Endplates

BACKGROUND AND OBJECTIVES

Myasthenia gravis (MG) can in rare cases be an autoimmune phenomenon associated with hematologic malignancies such as chronic lymphocytic leukemia (CLL). It is unclear whether in patients with MG and CLL, the leukemic B cells are the ones directly driving the autoimmune response against neuromuscular endplates.

METHODS

We identified patients with acetylcholine receptor antibody-positive (AChR⁺) MG and CLL or monoclonal B-cell lymphocytosis (MBL), a precursor to CLL, and described their clinical features, including treatment responses. We generated recombinant monoclonal antibodies (mAbs) corresponding to the B-cell receptors of the CLL phenotype B cells and screened them for autoantigen binding.

RESULTS

A computational immune cell screen revealed a subgroup of 5/38 patients with MG and 0/21 healthy controls who displayed a CLL-like B-cell phenotype. In follow-up hematologic flow cytometry, 2 of these 5 patients were diagnosed with an MBL. An additional patient with AChR⁺ MG as a complication of manifest CLL presented at our neuromuscular clinic and was successfully treated with the anti-CD20 therapy obinutuzumab plus chlorambucil. We investigated the specificities of expanding CLL-like B-cell clones to assess a direct causal link between the 2 diseases. However, we observed no reactivity of the clones against the AChR, antigens at the neuromuscular junction, or other common autoantigens.

DISCUSSION

Our study suggests that AChR autoantibodies are produced by nonmalignant, polyclonal B cells The new anti-CD20 treatment obinutuzumab might be considered in effectively treating AChR⁺ MG.

CLASSIFICATION OF EVIDENCE

This is a single case study and provides Class IV evidence that obinutuzumab is safe to use in patients with MG.

Secondary autoimmune cytopenias in chronic lymphocytic leukemia

Secondary autoimmune cytopenias in chronic lymphocytic leukemia are distinct clinical entities that require specific management. These autoimmune disorders have a complex pathogenesis that involves both the leukemic cells and the immune environment in which they exist. The mechanism is not the same in all cases, and to varying degrees involves the chronic lymphocytic leukemia (CLL) cells in antibody production, antigen presentation, and stimulation of T cells and bystander polyclonal B cells. Diagnosis of autoimmune cytopenias can be challenging as it is difficult to differentiate between autoimmunity and bone marrow failure due to disease progression. There is a need to distinguish these causes, as prognosis and treatment are not the same. Evidence regarding treatment of secondary autoimmune cytopenias is limited, but many effective options exist and treatment can be selected with severity of disease and patient factors in mind. With new agents to treat CLL coming into widespread clinical use, it will be important to understand how these will change the natural history and treatment of autoimmune cytopenias.

Incidence and description of autoimmune cytopenias during treatment with ibrutinib for chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is frequently complicated by secondary autoimmune cytopenias (AICs). Ibrutinib is an irreversible inhibitor of Bruton's tyrosine kinase approved for the treatment of relapsed CLL and CLL with del(17p). The effect of ibrutinib treatment on the incidence of AIC is currently unknown. We reviewed medical records of 301 patients treated with ibrutinib, as participants in therapeutic clinical trials at The Ohio State University Comprehensive Cancer Center between July 2010 and July 2014. Subjects were reviewed with respect to past history of AIC, and treatment-emergent AIC cases were identified. Before starting ibrutinib treatment, 26% of patients had experienced AIC. Information was available for a total of 468 patient-years of ibrutinib exposure, during which there were six cases of treatment-emergent AIC. This corresponds to an estimated incidence rate of 13 episodes for every 1000 patient-years of ibrutinib treatment. We further identified 22 patients receiving therapy for AIC at the time ibrutinib was started. Of these 22 patients, 19 were able to discontinue AIC therapy. We found that ibrutinib treatment is associated with a low rate of treatment-emergent AIC. Patients with an existing AIC have been successfully treated with ibrutinib and subsequently discontinued AIC therapy.

A 61-year-old man presented with myopathy, neuropathy, and inflammatory dermatitis responsive to chronic lymphocytic leukemia treatment

The prevalence of paraneoplastic neurologic syndrome in cancer is 0.01%. Neurological syndromes can be seen in chronic lymphocytic leukemia (CLL) and mostly present as either leukemic infiltration of the central nervous system (CNS) or progressive multifocal leukoencephalopathy. To our knowledge, this is the first reported case of combined sensory-motor neuropathy, myopathy, and dermatitis in a patient with CLL.

Natural human antibodies to pneumococcus have distinctive molecular characteristics and protect against pneumococcal disease

The molecular and functional characteristics of natural antibody from the preimmune repertoire have not been explored in detail in man. We describe seven human IgM monoclonal antibodies selected on the basis of pneumococcal polysaccharide binding that share both molecular and functional characteristics with natural antibody, suggesting a common B cell lineage origin. Unlike class-switched antibodies, which are serotype-specific, the antibodies were polyreactive and bound all pneumococcal polysaccharide capsular serotypes tested. Some bound endogenous antigens, including blood group antigens and intermediate filament proteins. All the antibodies used unmutated heavy chain V (IGHV) that are expressed at an increased frequency in the elderly and in the preimmune repertoire. The CDR3 was characterized by long length (mean aa 18.4 (+/-4.2) and selective use of IGHD6 (P < 0.001) and IGHJ6 (P < 0.01) family genes. The clones expressing IGHV1-69 and IGHV 3-21 provided significant passive protection against invasive pneumococcal disease in vivo.

Autoimmune hemolytic anemia preceding T-ALL in a five-year-old girl

A 5-year-old girl developed acute lymphoblastic leukemia (T-ALL) 15 months after being diagnosed with autoimmune hemolytic anemia (AHA), while AHA was in partial remission. AHA was mediated by warm antibodies. Because AHA could not be controlled during the induction therapy of ALL, she was administered immunoglobulin G and plasmapheresis was performed. Hepatomegaly dissappeared in the 4th month. However, anemia requiring blood transfusion, positive direct Coombs' test, and splenomegaly dissappeared in the 13th month of the leukemia treatment; reticulocytosis and decreased haptoglobin level persisted. AHA exacerbated in the 24th month of the ALL therapy. Prednisolone was started but the family refused to continue the therapy. This case presents some features that were not reported before, such that ALL was preceded by AHA and involved T-cell lineage, AHA was mediated by warm antibodies, and the two disorders took place in childhood.