Is immune escape via human leukocyte antigen expression clinically relevant in chronic lymphocytic leukemia? Focus on the controversies.

Changes in classical and non-classical human leukocyte antigen expression by tumor cells can play a critical role in the generation of tumor antigen-specific immune responses and can modulate the interactions of natural killer cells and T cell subpopulations with target cells. Recently, several studies have investigated the relations between HLA molecules and prognosis in B-CLL, suggesting a potential clinical relevance of tumor escape mechanisms. In this paper, we will summarize conflicting information about the role of HLA-related prognostic factors in B-CLL, such as downregulation of HLA class I antigen expression, interactions between natural killer cell receptor and certain ligands and the role of HLA-G expression.