alpha-chymotrypsin and Burkitt-Lymphoma

A histone mixture (H1, H2A, H2B, H3, and H4) derived from calf thymus stimulated IgM production by human-human hybridoma HB4C5 cells. On the contrary, the histone mixture did not increase IgM production by the human Burkitt's lymphoma cell line NAT-30, IgG production by the human B lymphoblastoid cell line HMy-2, and IgE production by the human myeloma cell line U266. The immunoglobulin production-stimulating activity of the histone mixture was inactivated by trypsin or chymotrypsin digestion. In addition, confocal laser microscopic analysis had shown that HB4C5 cells incorporated a lot of histone but other cell lines did not incorporate it as much. These facts strongly suggest that histone acts as an immunoglobulin production-stimulating factor (IPSF) after internalization into the human B cell lines and the native structure of histone is required for the IPSF activity.

Topics: Animals; B-Lymphocytes; Burkitt Lymphoma; Cattle; Chymotrypsin; Dose-Response Relationship, Drug; Flow Cytometry; Histones; Humans; Hybridomas; Immunoglobulin M; Multiple Myeloma; Protein Binding; Protein Conformation; Protein Transport; Thymus Gland; Trypsin; Tumor Cells, Cultured

Ligation of the antigen receptor on B cells induces the rapid phosphorylation of tyrosine on a number of cellular proteins. A monoclonal antibody that recognized a tyrosine-phosphorylated cell surface protein that was present in activated B cells was generated. Amino acid sequence analysis showed that this 140-kilodalton protein was CD22, a B cell-specific cell surface glycoprotein and putative extracellular ligand of the protein tyrosine phosphatase CD45. Tyrosine phosphorylation of CD22 may be important in B cell signal transduction, possibly through regulation of the adhesiveness of activated B cells.

Topics: Antigens, CD; Antigens, Differentiation, B-Lymphocyte; B-Lymphocytes; Burkitt Lymphoma; Cell Adhesion Molecules; Chymotrypsin; Humans; Immunoblotting; Immunosorbent Techniques; Lectins; Lymphocyte Activation; Peptide Mapping; Phosphorylation; Phosphotyrosine; Sialic Acid Binding Ig-like Lectin 2; Signal Transduction; Tumor Cells, Cultured; Tyrosine

We have isolated a cDNA clone for an interferon-induced 15-kDa protein. The cDNA clone was prepared from mRNA isolated from interferon-beta-treated human Daudi cells. The clone of 635 base pairs contains an open reading frame coding for a protein of 145 amino acids, and suggests for the mRNA a 75-base pair 5' untranslated and a 125-base pair 3' untranslated region. Approximately 85% of the amino acid sequence of the 15-kDa protein has been independently obtained from 2 nmol of material using microsequencing technology on the N terminus of the intact protein and on tryptic and chymotryptic peptides. The amino acid sequence of the isolated protein is identical to the amino acid sequence deduced from the cDNA. Northern blot analysis confirmed that the mRNA for the 15-kDa protein is undetectable in untreated cells, but is greatly induced following interferon treatment.

Topics: Amino Acid Sequence; Base Sequence; Burkitt Lymphoma; Cell Line; Chymotrypsin; Cloning, Molecular; DNA; Genes; Humans; Interferon-gamma; Molecular Weight; Peptide Fragments; Proteins; RNA, Messenger; Trypsin

Topics: Animals; Antibodies, Heterophile; Antibody Specificity; Binding Sites; Bromelains; Burkitt Lymphoma; Catalase; Cats; Cattle; Cell Membrane; Chymotrypsin; Columbidae; Dogs; Ducks; Endopeptidases; Erythrocytes; Galactose; Galactosidases; Geese; Hemadsorption Inhibition Tests; Hemagglutination Inhibition Tests; Hemagglutination Tests; Humans; Lectins; Lung; Neuraminidase; Papain; Peptide Hydrolases; Rabbits; Swine; Trypsin