No abstract

In the periphery, B cells differentiate in germinal centres (GCs) of secondary lymphoid organs. Isolated GC cells die quickly in vitro by apoptosis. Therefore, cell lines originating from follicular lymphomas, which are the malignant counterparts of GC B cells, would provide a stable in vitro model to study the immunobiology of GC B cells. We have established three novel human follicular lymphoma cell lines that were characterized with special reference to immunophenotypic features, response to B-cell receptor (BCR) triggering, response to cytokines and cytokine mRNA expression. One of the cell lines, HF-1A3, has a phenotype of a centrocyte. It expresses surface immunoglobulin G (sIgG) and dies by apoptosis following BCR cross-linking. Co-stimulation with interleukin-6 (IL-6), IL-15 or interferon-g (IFN-g) rescues HF-1A3 cells from BCRinduced apoptosis. The second cell line, HF-28, also represents phenotypically an IgG þ centrocyte. Ligation of its BCR leads to the cell-cycle arrest at G1 instead of apoptosis. HF-28 cells express both CD45RA and RO isoforms, which is unusual in B lymphocytes apart from plasma cells, thus suggesting a transition to plasma cell phenotype. The third cell line, HF-4.9, which phenotypically represents an sIgM þ centroblast, responds by proliferation to BCR cross-linking. These cell lines offer a unique in vitro model to study antigenic selection and cytokine-mediated growth regulation of human GC B cells.

We have labelled the exposed surface glycoproteins of human blood T- and B-lymphocytes and cells from patients with chronic lymphocytic leukemia by the galactose oxidase-tritiated sodium borohydride method. The labelled glycoproteins were separated by polyacrylamide slab gel electrophoresis and visualized by autoradiography. The T- and B-lymphocytes show different and characteristic surface glycoprotein patterns. The surface glycoprotein patterns of the leukemic cells differ from those of normal, non-malignant lymphocytes. A relationship between the altered surface glycoprotein pattern of leukemic cells and the expression of leukemia-associated antigens is discussed.

A single PNA test in its present form is as sensitive an indicator of colorectal neoplasia as Hemolex completed over three days, but lacks specificity. The 160 kD cancer-associated antigen we have identified is under further characterization for development of a more specific PNA test.