Gastric extranodal marginal zone B-cell lymphomas of MALT type exclusively express toll-like receptor 4 in contrast to other lymphomas infiltrating the stomach

Background: Development and growth of extranodal marginal zone B-cell lymphomas (eMZBCLs) of mucosa-associated lymphoid tissue (MALT) type are thought to be highly dependent on Helicobacter pylori and autoantigens. Receptors mediating these effects are not characterised so far. Toll-like receptors (TLRs) recognise bacterial proteins and autoantigens, which results in inflammatory reactions and influences tumour development and growth. Materials and methods: TLR4, 5 and 9 expressions were evaluated by immunohistology and confocal microscopy in gastric eMZBCL in comparison to other lymphomas infiltrating the stomach. Results: TLR4 was exclusively expressed on the cell surface in all eMZBCL (n = 19) and not in chronic lymphocytic leukaemia (CLL, n = 12) or mantle cell lymphoma (MCL, n = 10). TLR5 was strongly expressed in CLL and weak in some eMZBCL (15 of 19), but not in MCL. TLR4, 5 and 9 were negative in all the three lymphoma entities. Conclusions: Exclusive TLR4 expression may enable eMZBCL to interact with H. pylori and autoantigens. Blockade of TLR4 might be a new approach for therapy of eMZBCL of MALT type.