RESUMO
BACKGROUND: Malignant B cells from patients with chronic B lymphocytic leukemia (B CLL) generally express both surface IgM and the pan T cell antigen CD5, a characteristic of the B1 population of B lymphocytes. The IgM on the surface of these B CLL cells is frequently polyreactive with respect to its capacity to recognize multiple structurally dissimilar antigens (Ag). OBJECTIVES: To understand the structural characteristics of the polyreactive binding sites of human IgM molecules expressed on B CLL cells by: (1) analyzing the nucleotide and protein sequences of the variable (V) domains of five IgM molecules expressed in cases of B CLL and; (2) utilizing these sequences to generate three-dimensional (3D) models of Fv (VL - VH) molecules. STUDY DESIGN: Peripheral blood leukocytes obtained from five cases of B CLL were tested for polyreactive binding properties by assessing their capacity to bind mouse IgG by indirect immunofluorescence. The V region genes of light and heavy chains were amplified using the polymerase chain reaction, subsequently cloned and their nucleotide sequences obtained. Translated amino acid sequences of the V domains were used to generate homology models of the Fv molecules. RESULTS: Low affinity binding of mouse IgG was demonstrated for all B CLL samples examined, confirming the polyreactive nature of the IgM expressed on these cells. There was an absence or minimal mutation within V region genes when compared to germline Ig genes. Junctional diversity was not observed for VL regions, although truncations and insertions were frequent in D minigenes of VH regions. The binding sites were predicted to form either relatively flat surfaces with occasional protrusions or cavities at the VL - VH domain interface. Aromatic side chains covered a large proportion of the potential binding surfaces in the models of B CLL Fv components. DISCUSSION: Primary DNA sequences can be categorized as germline, suggesting that the B cells involved in B CLL are germline or naive in origin. The medium to large HCDR3s provide the majority of probable contact residues for antigens. While prominent aromatic residues are likely to engage in binding patterns which are conserved (e.g. mouse Ig reactivity), the diverse binding sites predicted for B CLL-derived IgMs also have properties which are conducive to polyreactive antigen binding.
Assuntos
Anticorpos Antineoplásicos/química , Imunoglobulina M/química , Leucemia Linfocítica Crônica de Células B/imunologia , Sequência de Aminoácidos , Animais , Anticorpos Antineoplásicos/genética , Anticorpos Antineoplásicos/imunologia , Afinidade de Anticorpos , Sequência de Bases , Sítios de Ligação de Anticorpos , Antígenos CD5/imunologia , Genes de Imunoglobulinas , Humanos , Cadeias Pesadas de Imunoglobulinas/química , Cadeias Pesadas de Imunoglobulinas/imunologia , Cadeias Leves de Imunoglobulina/química , Cadeias Leves de Imunoglobulina/imunologia , Imunoglobulina M/genética , Imunoglobulina M/imunologia , Região Variável de Imunoglobulina/química , Região Variável de Imunoglobulina/genética , Região Variável de Imunoglobulina/imunologia , Camundongos , Modelos Moleculares , Dados de Sequência Molecular , Mutação , Conformação ProteicaRESUMO
The sera of 30 patients with premature ovarian failure (POF) and a control group of 19 menopausal women were screened for anti-ovarian and other tissue antibodies. Anti-ovarian antibodies were detected by indirect immunofluorescence using monkey ovary substrates from two different commercial sources. Serum anti-ovarian antibodies were detected in only one of the patients with POF. This test does not appear to be reliable for the detection of serum anti-ovarian antibodies, and the clinical usefulness of screening patients with POF for anti-ovarian antibodies is questionable.
