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Surface Ig (sIg) of follicular lymphoma (FL) is vital for tumor cell survival. We found previously that the Ig in FL is unusual, because the variable region genes carry sequence motifs for N-glycan addition. These are introduced by somatic mutation and are tumor specific. Unexpectedly, added glycans terminate at high mannose, suggesting a potentially important interaction of FL cells with mannose-binding lectins of the innate immune system. We have now identified mannosylated IgM at the surface of primary lymphoma cells. Recombinant lectin domains of the mannose receptor (MR) or DC-SIGN bind mannosylated Igs in vitro and bind to FL cells, signaling sIgM-associated increases in intracellular Ca²⁺. Lectins also bind to normal B cells but fail to signal. In contrast, anti-Ig signaled similarly in both FL and normal B cells. Mannosylation patterns were mimicked by FL Ig-derived single-chain Fvs (scFv), providing probes for potential receptors. Mannosylated scFv bound specifically to the lectin domains of the MR and DC-SIGN and blocked signaling. Mannosylated scFv also bound to DC-SIGN on the surface of dendritic cells. This unique lymphoma-specific interaction of sIg with lectins of innate immunity reveals a potential route for microenvironmental support of tumor cells, mediated via the key B-cell receptor.

Follicular lymphoma (FL) is a heterogeneous and incurable disease. One of the hallmark features of FL cells is the introduction of N-glycosylation (N-gly) amino acid sequence motifs into the immunoglobulin variable (IgV) region through ongoing somatic hypermutation (SHM) in the early stages of lymphoma development. These N-gly motifs, containing oligomannoses, are rarely found in healthy B cells but evidently play a crucial role in the clonal evolution and survival of FL cells in the hostile environment of germinal centers. The random nature of the ongoing SHM in FL occasionally results in the loss of productive immunoglobulin (Ig) genes or the elimination of N-gly motifs in productive genes. Such events typically lead to clonal deletion, as demonstrated by the longitudinal analysis of FL samples. However, rare N-gly-negative subclones demonstrate prolonged survival with evidence of ongoing SHM, giving rise to new N-gly-negative subclones before eventual deletion. This observation suggests the presence of specific mechanisms supporting their survival and proliferation. This perspective examines the current literature and explores whether a detailed transcriptomic and functional comparison of FL subclones characterized by different N-gly statuses, with a particular focus on N-gly-negative subclones, will lead to a comprehensive understanding of both N-gly-dependent and independent pro-survival and proliferative transcriptional signatures. Specifically, it aims to deepen our understanding of FL pathobiology and identify novel therapeutic targets for better disease management.

Chronic lymphocytic leukaemia (CLL) cells require micorenvironmental support for their proliferation. This can be recapitulated in highly immunocompromised hosts in the presence of T-cells and other supporting cells. Current primary CLL xenograft models suffer from limited duration of tumour cell engraftment coupled with gradual T-cell outgrowth. Thus, a greater understanding of the interaction between CLL and T-cells could improve their utility. In this study, using two distinct xenograft models, we investigated whether xenografts recapitulate CLL biology including natural environmental interactions with B-cell receptors and T-cells and whether manipulation of autologous T-cells can expand the duration of CLL engraftment. We observed that primary CLL xenografts recapitulated both the tumour phenotype and T-cell repertoire observed in patients and that engraftment was significantly shorter for progressive tumours. Reduction of patients’ T-cells to 2-5% of the initial T-cell number or specific depletion of CD8+ cells extended the limited xenograft duration of progressive cases to that characteristic of indolent disease. We conclude that manipulation of T-cells can enhance current CLL xenograft models expanding their utility for investigation of tumour biology and pre-clinical drug assessment.