Anti-CD79B monoclonal antibody, clone T3

Antigen-dependent activation of B lymphocytes is mediated through surface immunoglobulins and their associated molecules Ig-alpha (CD79a, Mb1) and Ig-beta (CD79b, B29). Here we show that an antibody directed against the extracellular part of human Ig-beta can, when cross-linked by CD32-transfected L cells, induce an IL-2-dependent proliferation of tonsil B cells. With the use of L cells stably transfected with both CD32 and CD40L, anti-Ig-beta activation of B cells was combined with CD40 triggering, an important component of the T cell-dependent B cell activation. This dual cellular activation resulted in two different phases, with initially synergistic proliferative effects, both without and with IL-2 or IL-10. Then, after 5-6 days of culture, cells stimulated with both anti-Ig-beta and CD40L underwent massive cell death, in contrast to B cells activated with CD40L alone. Cell death was not prevented by the addition of IL-2 or IL-10, but was prevented by the addition of Il-4. These results are discussed in the context of positive and negative selection of mature B cells.

Purpose: Relapsed or refractory diffuse large B-cell lymphoma (rrDLBCL) is fatal in 90% of patients, and yet little is known about its biology. Experimental Design: Using exome sequencing, we characterized the mutation profiles of 38 rrDLBCL biopsies obtained at the time of progression after immunochemotherapy. To identify genes that may be associated with relapse, we compared the mutation frequency in samples obtained at relapse to an unrelated cohort of 138 diagnostic DLBCLs and separately amplified specific mutations in their matched diagnostic samples to identify clonal expansions. Results: On the basis of a higher frequency at relapse and evidence for clonal selection, TP53, FOXO1, MLL3 (KMT2C), CCND3, NFKBIZ, and STAT6 emerged as top candidate genes implicated in therapeutic resistance. We observed individual examples of clonal expansions affecting genes whose mutations had not been previously associated with DLBCL including two regulators of NF-kappa B: NFKBIE and NFKBIZ. We detected mutations thatmay be affect sensitivity to novel therapeutics, such as MYD88 and CD79B mutations, in 31% and 23% of patients with activated B-cell-type of rrDLBCL, respectively. We also identified recurrent STAT6 mutations affecting D419 in 36% of patients with the germinal center B (GCB) cell rrDLBCL. These were associated with activated JAK/STAT signaling, increased phospho-STAT6 protein expression and increased expression of STAT6 target genes. Conclusions: This work improves our understanding of therapeutic resistance in rrDLBCL and has identified novel therapeutic opportunities especially for the high-risk patients with GCB-type rrDLBCL. (C) 2015 AACR.