Biased Use of the IGHV4 Family and Evidence for Antigen Selection in Chlamydophila psittaci-Negative Ocular Adnexal Extranodal Marginal Zone Lymphomas

Abstract

Extranodal marginal zone lymphomas (EMZL) are the most common lymphomas in the ocular adnexa. The etiology and potential role for antigenic stimulation in these lymphomas are still controversial. We have examined IGHV gene usage and mutations in 67 Chlamydophila psittaci-negative ocular adnexal EMZL. Clonal IGHV gene sequences were identified in 43 tumors originating from the orbit (19), conjunctivae (18) and lacrimal gland (6). Forty four potentially functional clonal IGHV gene sequences were detected with overrepresentation of the IGHV4 family and IGHV4-34 gene. All but 3 sequences were mutated with the average percent homology to the germ line of 93.5±6.1. Multinomial model and Focused binomial test demonstrated evidence for positive and/or negative antigen selection in 59% of the potentially functional IGHV genes. Intraclonal variation was detected in 8 of 11 tumor specimens. Overall our findings demonstrate that C. psittaci-negative ocular adnexal EMZL exhibit biased usage of IGHV families and genes with evidence for intraclonal heterogeneity and antigen selection in multiple tumors, implicating B-cell receptor-mediated antigen stimulation in the pathogenesis of these lymphomas.

Chlamydophila psittaci-negative ocular adnexal marginal zone lymphomas express self polyreactive B-cell receptors

“…11,12 Touchdown enzyme time-release PCR for the detection of C. psittaci DNA was performed as previously reported by us. 13 All studies were approved by the University of Miami Institutional Review Board.…”

“…[17][18][19][20] We have previously demonstrated a biased IGHV (IGHV4 family and IGHV4-34 gene) and IGKV (IGKV3-20) usage and the presence of extensive somatic mutations in IGHV genes in OAEMZLs that corresponded to positive and/or negative antigen selection pressures. 11,12 These findings pointed to a potential role for BCR signaling in the pathogenesis of C. psittaci-negative OAEMZLs and raised the hypothesis that possible shared tumor antigens may activate and promote the survival of these lymphomas. Detection of intraclonal heterogeneity in these tumors further suggested the existence of continuous antigen stimulation.…”

“…6,7 Although the pathogenesis of MALT lymphomas in these anatomic locations has been extensively studied, 8,9 the pathogenesis and etiology of ocular adnexal EMZLs (OAEMZLs), the second most common EMZL and the most common tumor occurring in the ocular adnexa, are still controversial. 1,[10][11][12] Chlamydophila psittaci infection was implicated in the pathogenesis of OAEMZLs, but this association demonstrated marked differences based on geography. 1,13,14 Most studies originating from North American institutions did not detect C. psittaci in OAEMZL tumors.…”

“…Detection of intraclonal heterogeneity in these tumors further suggested the existence of continuous antigen stimulation. 11 Previous studies of BCRs from EMZLs originating in the stomach and parotid gland demonstrated polyreactivity, binding to bacterial and self-antigens, including stomach extracts and DNA, and exhibited Ig rheumatoid factor (RF) activity. 21,22 However, the reactivity of BCRs derived from OAEMZLs has not been evaluated.…”

Identification of a novel stereotypic IGHV4-59/IGHJ5-encoded B-cell receptor subset expressed by various B-cell lymphomas with high affinity rheumatoid factor activity

“…All these lymphomas co-express a IGKV3-15/IGKJ1-encoded light chain, further indicating that they, indeed, represent a genuine newly identified stereotypic BCR group. Using the NCBI Protein-BLAST algorithm and literature IGHV searching, in addition, we also identified an ocular adnexal MALT lymphoma 17 and a DLBCL, 18 expressing highly similar VHCDR3s, encoded by IGHV4-59/IGHJ5 rearrangements ( Figure 1B). The frequency of this new stereotypic BCR group is high in the HCV-related lymphoma series of Ng et al 16 (3/19 = 15.8%) but low in DLBCL (1/483 = 0.2%) and in ocular adnexal MALT lymphoma (1/199 = 0.5%), whereas it has as yet not been identified in other B-cell lymphoma entities.…”