Primary CNS lymphoma B cell receptors recognize CNS proteins

Primary lymphoma of the central nervous system (PCNSL) is a diffuse large B cell lymphoma confined to the CNS. In order to elucidate its peculiar organ tropism, we generated recombinant antibodies (recAb) identical with the BCR of a series of 23 PCNSL from immunocompetent patients. While none of the recAb showed self-reactivity upon testing with common autoantigens, they recognized 1547 proteins present on a large-scale protein microarray. Interestingly, proteins recognized by the recAb are physiologically expressed by CNS neurons (GRINL1A, centaurin-α, BAIAP2). Furthermore, 87% (20/23) of the recAb including all antibodies derived from IGHV4 34 using PCNSL recognized galectin-3, which was upregulated on microglia/macrophages, astrocytes, and cerebral endothelial cells upon CNS invasion by PCNSL. Thus, PCNSL Ig may recognize CNS proteins as self-antigens. Their interaction may contribute to BCR signaling with sustained NF-κB activation and, ultimately, may foster tumor cell proliferation and survival. These data may also explain, at least in part, the affinity of the tumor cells of PCNSL to the CNS. Recombinant antibodies (recAb) identical with the BCR of a series of 23 PCNSL from immunocompetent patients.