Diffuse large B cell lymphoma is the most common type of non-Hodgkin lymphoma of which 40% present at extra-nodal sites including immune privileged sites such as the testis and the central nervous... Show moreDiffuse large B cell lymphoma is the most common type of non-Hodgkin lymphoma of which 40% present at extra-nodal sites including immune privileged sites such as the testis and the central nervous system (CNS). Loss of Human Leucocyte Antigen (HLA) expression has been described in many different tumour types as a mechanism to evade anti-tumour immune responsen. In testicular and CNS lymphomas HLA class I and II expression was very commonly observed in contrast to nodal, stomach and skin lymphomas that expressed HLA in most of the cases. Loss of HLA-DR and DQ expression was often due to homozygous deletions of the corresponding genes. Loss of class I expression was often caused by loss of Beta-2-microglobulin expression and hemizygous deletions. Despite their immune privileged status, the testicular and CNS lymphomas showed high numbers of activated cytotoxic T cells, suggesting that these lymphomas are highly immunogenic. DNA-typing for HLA-DR and DQ polymorphisms in testicular and nodal lymphomas revealed a positive association of testicular lymphomas with HLA-DRB1*12 and a negative association of nodal lymphomas with HLA-DRB1*07. Both testicular and nodal lymphomas showed a positive association with HLA-DRB1*15. No significant relationship was found between the different haplotypes and the occurrence of homozygous deletions in the testicular lymphomas. Show less
