An HLA Lost Mutation May Lead to Leukemic Relapse of Recipient Type Six Years After Bone Marrow Transplantation

Products of the major histocompatibility complex (MHC) serve to direct interactions amongst cells of the immune system. Cytolytic T cells recognize their targets by means of an antigen-specific receptor, but this recognition also requires a match of MHC antigens between effector and target cells (MHC restriction) [1]. Cytolytic T cells have been implicated in the elimination of malignantly transformed cells [2]. One mechanism by which tumor cells might escape immune destruction would be a reduction of the expression of MHC antigens, i.e., introduction of restriction elements. This situation occurs in cells transformed with an oncogenic strain of adenovirus which have switched off the expression of class I MHC antigens [3].