Ultrastructural and Immunologic Characteristics of Mouse × Cattle Xenogeneic Hybridomas Originating from Bovine Leukemia Virus-infected Cattle

Abstract

Abstract. Nine percent of xenogeneic hybridomas originating from a bovine leukemia virus (BLV)-infected cow secreted monoclonal IgM antibodies with multispecific reactivity. Similar reactivity was evident in some antibodies with an unusually long (Ͼ 50 amino acids) third complementarity-determining region of the heavy chain. Electron microscopy of hybridomas demonstrated the presence of c-type virus particles consistent with polymerase chain reaction detection of BLV env gene. Some hybridomas contained dilated rough endoplasmic reticulum and cisternae filled with moderately electron-dense granular substance compatible with plasma cells at presecretory stage. The number of chromosomes in xenogeneic hybridomas corresponded to the sum total of mouse and bovine chromosomes. None of the hybridomas showed polyploidy. The immunochemical and genetic analysis of stable bovine immunoglobulin-secreting xenogeneic hybridomas confirms that BLV infection causes polyclonal B cell activation regardless of antigen specificity. Presence of c-type particles in hybridomas suggests that T cell-derived cytokines are not required for sustained BLV expression.

Conservation and diversity in the ultralong third heavy-chain complementarity-determining region of bovine antibodies

“…Questions remain as to how the bovine ultralong CDR H3 antibodies recognize antigen and what types of epitopes they recognize. Earlier work has indicated that the IgM antibodies BLV1H12 and BLV5B8 are multispecific, recognizing antigens such as DNA, synthetic haptens, and cytoskeleton proteins, and may be natural autoantibodies (1,42). Previous experiments with one ultralong antibody to the immunogen bovine viral diarrhea virus indicate that only CDR H3 is necessary for binding antigen (2).…”

VH and VL Domains of Polyspecific IgM and Monospecific IgG Antibodies Contribute Differentially to Antigen Recognition and Virus Neutralization Functions

“…Antigen specificity of the Ab fragments was determined by ELISA against a panel of test Ags that included bovine actin, bovine thyroglobulin, bovine ubiquitin (all from Sigma, St. Louis, MO, USA), bovine IgG1 (Bethyl laboratories, Montgomery, TX, USA) and recombinant mycobacterial heat shock protein 65 (rHSP65; UNDP/WHO program, Geneva Switzerland). These antigens are known to be recognized by polyspecific BLV1H12 IgM antibody .…”