Triggering of neoplastic B cells via surface IgM and the cell surface antigens CD20 and CDw40. Responses differ from normal blood B cells and are restricted to certain morphologic subsets

Abstract

By raising monoclonal antibodies (MAbs) against B cells, a number of cell surface molecules have recently been identified which after binding by their specific antibody can trigger B cells, either alone or in co-operation with antibodies to surface immunoglobulin (sIg). The anti-CD20 (Bp35) MAb IF5 can deliver a strong activation signal to resting normal B cells, and the anti-CDw40 (Bp50) MAb G28-5 can promote activated G1 B cells to enter S phase. These antibodies were tested for their functional effects in vitro on suspended cells from 17 follicle-center-cell (FCC) lymphomas, 5 cases of chronic lymphatic B-cell leukemia (B-CLL) and 8 cases of various histological types. Changes in cellular volume, RNA and DNA synthesis were compared with the results obtained with a polyclonal anti-mu [F(ab')2] antiserum, a MAb to surface IgM (AF6), 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and B-cell growth factor (low-molecular-weight BCGF). Our data reveal differences in the requirements for triggering of various B-cell subsets: cells from CLL responded strongly to TPA but not to anti-mu, which is a potent stimulator not only of normal B cells but also of cells from individual cases of FCC lymphomas. Our observations suggest that the differentiation stage of B-CLL cells is distinct from that of small resting B cells from peripheral blood. Centrocytic lymphomas could not be activated by any of the reagents. CD20-mediated triggering was seen in neoplastic B cells from only 4 of 30 cases, indicating that most B-cell neoplasias were not responsive to this activation pathway. In contrast, the anti-CDw40 MAb consistently stimulated DNA synthesis together with anti-mu or TPA in cells from FCC lymphomas, but not from CLL. Together, these results suggest that activation in different neoplastic B-cell subsets depends on distinct signal transduction mechanisms.

Modulation of the CD40–CD40 ligand interaction using human anti‐CD40 single‐chain antibody fragments obtained from the n‐CoDeR phage display library

“…The filamentous phage gene3 fragment, which is fused to the single‐chain antibody fragment (scFv) in the library vector in order to enable display on the phage surface, was removed and the expression vector was transformed into SF110 cells 20 . As positive control we used variable domains from G28‐5, 21 cloned into a scFv expression vector (pFab5c) and produced in SF110. Cultures were grown in TB‐medium at 37° to OD 600 =0·5 and then induced with 0·1 m m isopropyl‐thio‐β‐D‐galactoside.…”

The TNF Receptor Superfamily in Co-stimulating and Co-inhibitory Responses

“…As a second mechanism of restricting immune responses, the TNFRSF member, HVEM activates an IgSF checkpoint receptor. Interestingly, cooperative signaling via TNF receptors were first recognized with the CD40 system, which enhanced the proliferation of antigen-activated B cells, driven by CD40 Ligand expression in helper CD4 + T cells (Beiske et al, 1988). Cosignaling in B cells is not limited to CD40 as critical survival signals for B cells provided by the BAFFR system underscores the essential nature of this receptor superfamily member in lymphocyte cosignaling (Mackay and Schneider, 2009).…”

In vitro beta2-microglobulin (β2m) secretion by normal and leukaemic B-cells: effects of recombinant cytokines and evidence for a differential response to the combined stimulus of phorbol ester and calcium ionophore

“…Based on their cytomorphological and surface antigen (SIg) features, B-CLL cells were originally considered as the malignant counterparts of small resting B-cells (Robert et al, 1986). However, recent functional studies suggested that B-CLL cells are arrested in an 'activated' state (Beiske et al, 1988) that is reflected by the expression of one or more activation-associated antigens such as FMC7, UCHB1, CD25, B5 or B7 (Table III). Furthermore, the morphology of B-PLL cells and B-CLL cells in 'prolymphocytoid transformation' (CLL-Pro) resembles that described for activated normal B-cells (Melo et al, 1986).…”