Tumor-infiltrating T cells with similar antigen binding sites in different mucosa-associated lymphoid tissue type B cell lymphomas.

B cell lymphomas of mucosa-associated lymphoid tissue (MALT)-type arise on the background of chronic inflammation due to either autoimmunity or infection at various sites of the organism. Characteristically the tumor-infiltrating T cells found in large numbers in MALT-type lymphomas are predominantly of CD4(+) phenotype and may have impact on tumor pathogenesis. To assess whether the chromosomal translocation t(11;18)(q21; q21) that is specific for at least a subset of MALT-type lymphomas may have an impact on tumor environment, we investigated the antigen binding sites of tumor-infiltrating T cells from one t(11;18)-positive tumor of the thyroid and one t(11;18)-negative tumor of the stomach. MHC Allelotyping was performed and revealed common alleles in HLA-DR and HLA-DQ loci. Cloning and sequencing of the complementary determining region 3 in V(beta2) chains of T cell receptors demonstrated the use of identical J(beta)segments in both patients, suggestive for recognition of the same antigen. We therefore suggest that tumor-infiltrating CD4(+) T cells are tightly integrated in MALT-type lymphoma immunoarchitecture irrespective of genetic background and localization of the tumors.