Which assay is characterized by direct allorecognition?

The assay characterized by direct allorecognition is the mixed lymphocyte reaction (MLR). In this context, direct allorecognition refers to the process by which recipient T cells recognize foreign MHC molecules on donor cells presented within the reaction.

During the MLR, peripheral blood lymphocytes from a donor, which express unique Human Leukocyte Antigen (HLA) types, are mixed with T cells from a recipient. The recipient's T cells are stimulated by the foreign MHC molecules on the donor cells. This interaction leads to the proliferation of T cells that recognize the foreign antigens, resulting in a cellular immune response. The MLR is valuable in transplant immunology as it helps to assess the immunogenicity of a graft and predict the likelihood of transplant rejection based on the degree of response elicited.

In contrast, the other assays mentioned do not primarily focus on direct allorecognition. The FXM (Fluorescence-activated cell sorting) primarily assesses the expression of specific cell surface markers rather than direct T-cell recognition. The SSO (Sequence-Specific Oligonucleotide) assay is utilized for genotyping and determining specific alleles but does not involve direct recognition by T lymphocytes. The AHG-